« Previous | Main | Next »

So what is 3DTV?

Post categories:

Andy Quested Andy Quested | 11:45 UK time, Wednesday, 8 June 2011

To give it it's proper name it's plano-stereoscopic (often known as Stereo 3D or S3D), an idea that's a lot older than television and even older than cinema sound!

Stereoscopy experiments began in the 19th century starting with still images but it rapidly followed the movies into the early cinemas. Stereo camera rigs were patented around 1900 and the earliest confirmed 3-D film (The Power of Love) was shown in the Ambassador Hotel Theatre Los Angeles in September 1922!

Over the past 90 years 3D has come and gone. After each decline there have been various attempts to revive the technology: The 1950's for example, were described as the golden age of 3D with now infamous "House of Wax" released in April 1953 with stereo sound!

The 1980s were responsible not just for big hair but for a run of "part III" films ripe for the addition of a "D" at the end of the title. Jaws 3-D, Amityville 3-D and Friday 13th Part III-D, all vying to throw various dismembered body parts over an eager audience!

Each revival was usually the result of a technical advance or technique that seemed to make 3D better or a more compelling but never enough to catch a mass sustainable market.

The BBC has made 3D content in the past. In 1993 Children in Need made a Doctor Who short using the Pulfrich effect . BBC Films made the very successful Streetdance 3D and BBC Worldwide has begun exploring 3D Natural History programmes. More recently we have tried 3D 6 Nations into cinema and a special Comic Relief Strictly Come Dancing promo.

And! I'm sure you all know Sky has its own 3D channel showing a mix of sport, movies, and concerts along with a collection of other genres.

Is 3D bad for you?

There has been an incredible amount of hype and misunderstanding about alleged risks from watching 3D. Stereo 3D gives an illusion of depth but your eyes are still focused on the screen plane no matter how far in or out an object actually is. This is where some of the confusion and possible "health scares" come from!

The RNIB has done some work evaluating the experience partially sighted people have when viewing 3D and an organisation called the International Telecommunications Union (ITU) - part of the UN, has asked the World Health Organisation to report on any effects associated with watching 3DTV.

After watching a lot of 3D television myself what I can say is, well-made 3D is an enjoyable experience, poor 3D can make you feel a bit odd and can give some people headaches but quite frankly you turn poor 3D off long before that!

This site has a good explanation of parallax - I will let you guess which of the four diagrams could cause discomfort!

Some other good links for further reading are;




How do 3D TVs work?

anaglyph glasses


Finally here's a very quick overview of different 3D displays and how they work but first we are not doing colour separation 3D or anaglyph!

Anaglyph, Color Code (and other colour variants) work by showing both left and right images at the same time, the left eye image one colour and the right eye image in another.



Coloured glasses make sure the images go to the appropriate eye.


colorcode glasses


Colour performance is very variable as is the 3D effect and it is difficult to focus properly on the image. After the glasses come off the world looks very strange (coloured glasses affect normal colour vision for a while) - Impossible to watch the without the correct version of the coloured glasses






Polarised Screen

polarised glasses


Requires a 3D TV with a polarised screen. The left and right eye images are lined up behind the polarising screen, each image is given a different polarisation. To see the 3D image polarised glasses are needed. These are similar to polarised sun glasses but the lens of each eye has a different polarisation to make sure the correct image goes to each eye.


Shuttered (above)

Shuttered technology requires two active components - the screen and the glasses. Shuttered LCD glasses are controlled by an infra-red signal sent from the TV. The Left and Right eye images are flashed alternately on the screen at a high frame rate (100 times a second or more). When the Left eye image is on screen the Right eye lens of the glasses is opaque and visi-versa.

At the moment glasses from different manufactures are incompatible so you need to have the right glasses for the TV you have.

3D TV with no glasses

The technology behind 3D TVs that do not need glasses is very similar to the old 3D plastic postcards. It is based on the work done around 1840 by Sir Charles Wheatstone.

The screen is covered with tiny lenses, arranged to send zones of left/right images to the viewer.

phillips 3d image


The lenses direct the left/right images out of the screen in zones. If you sit in a zone at the correct distance you see 3D - if you move out of a zone you lose the 3D image.

Lenticular screen technology is still very new but developing rapidly.

Philips (left) was an early pioneer of this technology for domestic displays.



I will try and keep you updated between now and the finals weekend if there is news or anything changes but I will give a full explanation of the production as soon as possible after the matches.

Andy Quested is Head of Technology, BBC HD & 3D, BBC Future Media & Technology


  • Comment number 1.

    From the article you quote from (Pulfrich effect):
    On Sunday, Jan. 22, 1989 the Super Bowl XXIII halftime show and a specially produced commercial for Diet Coke was telecast using this effect.

    I remember seeing this from a Umatic tape of the show that an edit facility in London had shortly afterwards. It was a rather strange experience and the live part must have been a bit of an issue to plan regarding cameras. From what I remember the effect only worked while the cameras were constantly dollied at a slow pace to the right. If a camera stopped moving it all went very flat (from the almost flat otherwise!).

    I have been quite disappointed with some of the shutter frame sysytems. I expect this is to do with latency of image linked with latency (or mis-timing?) of the glasses.

    Currently I am convinced that polarised is best, as long as you keep your head straight! Much cheaper as well if you need a dozen pairs of glasses!

  • Comment number 2.

    Dear Kit Green

    Thanks for the post - it was an "interesting" experience and one I actually edited! Yes the background had to keep moving - and as a reminder http://www.youtube.com/watch?v=VL87KAGY0_U

  • Comment number 3.

    It really is a different world, isn't it?

  • Comment number 4.

    Dear Joe K - thanks for the cryptic post - Doctor Who or 3D!

  • Comment number 5.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 6.

    I really don't like "3D". The cinema experience is less than pleasant, particularly for someone who already wears glasses and has to wear the 3D ones over the top of their own.

    You have to pay more to see a film with poorer contrast, lower resolution and brightness than the 2D version, all for the dubious "pleasure" of "3D", particularly if its the naff post-production faux-3D that is used in a lot of films (I see they are going to try to milk Titanic again with this trick).

    Given I find the cinema 3D experience to be poor, the domestic experience is worse, and certainly *not* a family experience. You have to sit fairly close to to, and right in front of, the screen to get the proper 3D effect. If you sit to one side the 3D effect starts to look weird. So you have to arrange your living room to suit (if you have the room), only one or two can enjoy the 3D and those viewers have to sit bolt-upright (no lounging around or getting comfortable).

  • Comment number 7.

    Can across this on You tube:

    Sir David Attenborough Talks BBC 3D Plans

    This guy really knows what he is talking about. He was the best channel head the BBC ever had. Compare his enthusiasm for 3D with the luke warm attitude of the present head of BBC 3D. It always amuses me that Danielle is the head of a channel which doesn't exist.

  • Comment number 8.

    Dear trevorjharris and welcome to the "what is 3D blog". It was a good session - you should really see (or hear) the rest of it. Good to know you would like us to do a lot more with 3D and maybe the crux of the clip you link to will turn out to be the method of delivery.


  • Comment number 9.

    To me the last statement David makes is the most profound "I am grateful to Sky for enabling me to do so". This sums up concisely what a 3D channel should be namely an enabler to enable creative people to create wonderful things. The BBC policy of "wait and see" is frustrating to both the creative and and the viewer alike. In fact it could be very damaging to the BBC as they could loose their most creative people to other broadcasters. As David says he moved to Sky becasue it was an opportunity he could not resist. It is not clear exatcly what the BBC is waiting for.

  • Comment number 10.

    Thanks trevorjharris - I think the interview goes some way to explain why we are not rushing and as our technical and editorial statements have said, we are trying and testing. I am sure you would be amongst the first to have a point of view about waste.

  • Comment number 11.

    The BBC has been "trying and testing" for the last 40 years. Infact John Logie Baird patented and demonstrated a 500 line colour 3D system in 1941. He also demonstrated a 1000 line system. The only experiment Sky had to do was to make sure the SbS system worked with the existing Sky box. It did and then went ahead and now Sky 3D is growing faster than HD when it started. One has to ask what test would the BBC have to do to make a 3D channel happen. The answer is of course there is no test the decision has nothing to do with "trying and testing". It is simply that the BBC management have chosen to not to invest in 3D but as David implies that they want to spend the money on other things. As I have said before there is very little experimental benifit from just taking a feed from Sony and delivering to a BBC channel. Sky has already demonstrated that it works.

    As for waste it depends what you mean by waste. Many people consider the incredable sums spent by the BBC for its move to Salford to be a complete waist of money not to mention the expenses claimed by the BBC Trust members. Others consider that running an HD transponder in DVB-S mode and also transmitting an enormous number a null bytes to be a waste. Some consider that transmitting an HD channel with low picture quality a waste. Infact the BBC is probably the most wastefull company other than the NHS that I know.

    Why would starting a 3D channel be a waste.

  • Comment number 12.

    Thanks for the overview on 3D TVs. I have tried reading up on various TV manufacturers but I'm not entirely sure which types the companies use. I'd love to buy a 3D TV like this one from Panasonic: http://www.panasonic.co.uk/html/en_GB/Products/VIERA+Flat+Screen+TV/VIERA+Overview/Panasonic+VIERA+3D/4916489/index.html but I'll think I'll wait a year for the technology to come down in price

  • Comment number 13.

    Post 11# I agree Trevor. Until now BBC had thought their funding was going to be coming from a open pot of unlimited funds(just like the NHS). They are not scutinised enough for previously wasting so much money. No need for a 3D test, if it's not going to be taken seriously. A working solution is already in place, why re-invent the wheel. As it is, the BBC are going to have to sacrifice when they have to make a 20% saving. And the trust still want to go begging for more money to save a channel.

  • Comment number 14.

    There is no point in setting up a 3D channel (and has HD investment been wasted) if TV Centre is going to become another shopping mall or the usual West London apartments.

  • Comment number 15.

    Dear mindem. Thanks for the post. The type of display technology is really up to your personal taste and how you watch (type of room, TV position etc etc.) Try a few out in the shops and see what you think. The display technology will keep developing so there will be more options in the future I'm sure!


  • Comment number 16.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 17.

    Hi - these comments are drifting into off topic areas. Can we please stick to the topic: which is 3DTV.


  • Comment number 18.

    I believe 3D TV is here to stay this time, we are seeing 3D game devises, phones and tablet now embracing this tech!.

    I work in the field of Augmented reality, and we are already seeing the potential of 3D through these devises! This new LG 3D Android Smartphone MUST be a winner when AR is in question.

    We are looking forward to seeing what is going to be developed for this cool phone using AR and other up and coming devises using 3D

    The LG Optimus 3D is the next step forward, especially with sky teaming up with LG to create content, not only that, youtube have also developed their 3D channel as well.

    I am also looking forward to seeing what the BBC is going to release in the way of 3D content!

    Chris Brookfield

    [Unsuitable/Broken URL removed by Moderator]

  • Comment number 19.

    Have to say I'm still not entirely convinced about 3D tv, can't get rid of the fuzzyness!

  • Comment number 20.

    Dear John Parkes, thanks for the post. Can you give me more details? Do you have a shuttered or polarised display and if you close each eye is the image better in the other? Andy

  • Comment number 21.


    I posted a version of this to the “Gearing up to deliver Wimbledon 3D” blog but there was no response, so thought I'd repeat here just in case...”

    Whilst I can understand the BBC providing split screen approach for the experimental 3D service now, do you expect the same method to be used in the future?

    The current 3D services are not compatible with 2D, so you have to provide duplicate services for both 2D and 3D viewers.

    If you have potentially loads of bandwidth available (such as on satellite or cable)this "doubling" of capacity is not so much of an issue (however, I recall the BBC's need to make efficiency savings), but on terrestrial there isn't such capacity available.

    According to Barry Fox in this month's What Satellite & Digital TV, in the US they are providing "depth based 3D" where a 2D HD signal is accompanied by an additional "helper" signal to provide depth information. One option is apparently to use MPEG's Multiview Video Profile where the left eye is broadcast if full 2D HD, with a right eye view reconstructed from the separate signal. The bandwidth demand is less but the receiver has to have a dual decoder.

    This sounds similar to FM Stereo encoding where a L+R signal is provide for mono radios and an additional L-R signal is available that can be used by stereo receivers to rebuild the separate L & R signals.

    It seems (to me at least) that the current 3D system is a short term "stop gap" using current HD satellite and cable receivers and that long term new "real 3D" receivers will be required if 3D is to ever really take off for anything more than an experimental service.

    Do you agree? If so, when would do you expect such enhanced 3D broadcast delivery services to start?

  • Comment number 22.


    I would agree with you that SbS should hopefully be a short term "stop gap" as stream compatable can give better quality pictures.

    The BBC has made it clear that it has no plans for a 3D service. This is very worrying in that if they do start a 3D service it will probably be a rushed job like BBC One HD. After all the BBC still do not provide a proper HD service let alone 3D.

    The people you should be asking is Sky. I wonder if the new Sky boxes may the capable of supporting SC 3D but I just don't know. I would expect new HD channels to be made available soon such as ITV 3D, Eurosport 3D and Discovery 3D.

  • Comment number 23.

    Dear thegrail thanks for the post and sorry if I missed the post on the Wimbledon blog. You are talking about frame and service compatible 3D. Have a look at http://tech.ebu.ch/news/3d-tv-frame-compatible-top-up-system-d-19feb10

    The Side by Side option works through the current broadcast infrastructure including transmission and set top box without change, this means no additional cost to you or us - well that's assuming you have a 3D TV. You have to remember at the moment the 3D and 2D versions of a programme are different and therefore we need two channels no matter what the transmission technology. Wimbledon will even have two commentaries to match the different coverage.

    This year BBC One HD is carrying the finals and BBC HD should have been transmitting the promo during the afternoon - therefore it's ideally placed for a bit of a trial transmission.

    There are many different experiments with 2D plus depth and full twin image transmission - have a look at

    Synchronising streams is something BBC R&D has been working on for a while too and this technology will open up lots of options in the future.

    The trouble with many of the so called next generation 3D technologies is they may need new set top boxes or even TVs.

    There is also the issue of production cost. Until we can make 2D and 3D programmes with the same camera, 3D production will be limited to the special or high profile events or programmes that attract a very big international sales.

    Dear trevorjharris thanks for the post. We have said we have no plans for a 3D channel at the moment. There are better ways to deliver occasional or alternate versions of programmes.


  • Comment number 24.

    Glad to hear no plans for a separate channel. As one of the significant minority (I believe around 12-15% of the population) who are unable to see 3D TV/films (in my case due to a sight problem) I really don't want large chunks of content moving off to only be viewable in 3D. Colour and HD were improvements to existing systems, usable by all existing viewers who bought into the technology - 3D is totally different and I for one will be glad if it yet again fails!!

  • Comment number 25.

    @Alan Robertson

    No one is proposing that any content will only be available in 3D. As Andy says if a "Service Compatable" system is adopted th viewer will have the choice of 2D or 3D. 3D has never "failed" and 3D films have been produced for years. John Logie Baird patented a colur 3D system in 1941. The difference this time is that it has a very high profile and greatly improved technology. Given that 2D versions will be available I don't know why you should be glad if it fails. After all some people are colour blind does that mean we should all be watching in black and white.

    Chris John Sky's chief engineer believes that 3D will become that "Prime viewing choice" and they are puting £380 million into 3D production this year. He also notes that 3D is groing as fast as HD did at the begining.


    The "sitting on the fence" stance by the BBC is not because the BBC does not believe 3D will be successful it is just thay they prefer to spend our money on other projects such as the move to Salford and other building projects. Any one who wants to stay with Free to Air services are not going to invest in 3D for the occasional broadcast.

    The biggest danger is that the BBC will loose thier most creative program makers to 3D broadcasters. They have all ready lost David Attenborough to Sky because he could not resist the challenge of a new medium.

  • Comment number 26.


    The Sky (marketing?) guy only said "a good portion of that will be spent on new 3D productions which will need to evolve into genres outside of sports such as gameshows and pop videos to reduce the content gap".

    The £380m is across all Sky production - not just on 3D. And it implied that most of the spend will still be on sport which seems to be the main reason people are going for 3D (apart from rumours about "adult").

    Sky are (naturally) pushing 3D as a marketing differentiator - and as a revenue source - you need to spend over £62 per month with Sky to get the (single) Sky 3D channel.

  • Comment number 27.

    @trevorjharris good points, however my concern is that things will start to become 3D-only, or filmed specifically to take advantage of that and look worse in 2D. As bandwidth becomes tight (or because broadcasters such as Sky want to ram 3D down viewers throats), will we be forced to have a 3D TV to watch the latest channels, even if you don't want to watch them in 3D? A 2D TV can't cope with the side-by-side trasmission and displays it as such, presumably a 3D TV can just display one of the two - but why should I have to buy a 3D TV when I'm not going to gain any benefit from it?

    My view is perhaps coloured by recent trips to theme parks where 3D is the latest "big thing" and much of the ride relies on that aspect - for those that can't see it, it makes it a pretty poor ride (as they have just relied on the 3D element rather than building in something decent).

  • Comment number 28.

    Sorry you are right it is across all Sky production with a "good proportion" going on 3D.

    @Alan Robertson

    Yes Sky see 3D as a new revenue stream. That is one of the problems in that the BBC will get thier licence fee whether they innovate or not. They just see 3D as an extra expense. The BBC's main concern in research is to make TV cheaper rather than better.

    Actually there are stream compatable 3D systems designed to work with existing 2D televisions so you will not have to buy a 3D tv.

  • Comment number 29.


    You will have to pay over £750 per year in addition to the £145 license fee per year to get the 1 Sky 3D channel. I humbly suggest that those going for 3D in a big way now are the typical early adopters who have lots of money to spare.

    The BBC have been told they will get no increase in license fee and will have to make savings in the coming years, as well as taking on new costs (such as the World Service). The BBC have to cost justify any expense. Yes - the BBC do not see 3D as a revenue stream so is unlikely to do it until there is a business need for the BBC - maybe in these tight economic times when there is sufficient license fee payer demand – not just because it is “trendy” or “Sky is doing it”.

    I (personally) am quite satisfied with the Freesat HD channels (now I have splashed out on a new DVB-S2 PC card - another topic) and only pay the annual £145 license fee.

    To me wasting our license fee on a permanent 3D channel that few have receivers for and what may turn out to me a "white elephant”, would be a big mistake.

    It seems people are losing interest in 3D as sales of 3D versions of blu-ray are dropping: http://www.reghardware.com/2011/05/24/yanks_3d_slump/

    Some people want to watch 2D instead of 3D: http://www.reghardware.com/2011/06/06/glasses_change_3d_back_to_2d/

    And those buying new TVs aren't that interested in 3D anyway: http://www.reghardware.com/2011/06/08/3d_led_internet_not_selling_tvs/

    When a standard stream compatible 3D system is finally agreed amongst manufacturers (perhaps the DTG?) then maybe have 3D - but for now I agree it would be a waste for the BBC to do anymore than an experimental service.

  • Comment number 30.

    Fantastic blog information Andy. As a Sky viewer of 3D and blu-ray I will be switching between Freeview and Sat to see if there is a difference - I don't think there will be any though!
    I remember the Dr Who special - it followed on from RTL's late night naughty quiz show in Germany with stripping contestants - all swishing about as the camera panned constantly to give the Pullrich 3D effect.
    You may be interested to learn that xPand 3D active shutter glasees now work with all major brands of 3D telly - so you can take them to a friends's house who may have a different make of set to you. They are also significantly better than the ones shipped with my LG set - less ghosting - loss of synch etc. A fantastic purchase. No, I don't work for them lol....

    Looking forward to the show....

  • Comment number 31.

    Thanks for the post Howard. Hope you enjoy the tennis this time with no (intentional) Pullrich effect! Glad you found some universal glasses and they really work!


  • Comment number 32.

    Seeing as you've already mentioned Doctor Who... Would it be possible to convert & broadcast the 1993 Children in Need episode, or the more recent 2010 series 3D trailer?

  • Comment number 33.

    Thanks brian_damage - it would be good but the Pulfrich system only produces 1 image and you don't need a 3D TV to see the 3D - so it really is the Pulfrich "effect"


  • Comment number 34.

    I'm loving the 3D tennis and can't wait for the gents final tomorrow (shame Murray isn't in it). Please show more major sports events in 3D please. Thank you. Jon Allcock from Redditch Worcestershire.

  • Comment number 35.

    Dear Jon - thanks very much for the comment - indeed looking forward to tomorrow


  • Comment number 36.

    Thank you Andy The information shared has greatly assisted me in developing prior knowledge on movie productions in 3D. However I am wary that this ongoing technology is inconsiderate to the needs of persons with significant eye defects. You implied that viewers would be compelled to turn off poor 3D because of the quality. This is merely an opinion. What about the cases of children who are fascinated by the technology regardless of the quality and proceed to watch it? How then can the public be reassured that these poor 3D films are prohibited from being broadcasted on public television?

  • Comment number 37.

    Dear Brian - thank you for the post. We do have a review process and all programmes are watched before they are transmitted - bad 3D will be questioned and rejected. Poor 3D is just that, not well made, also there is much contrary information around the impact of watching 3DTV (full stop). Have a look at the RNIB report mentioned in the blog.


  • Comment number 38.

    I am anxiously awaiting the update on this blog since the information brought forward was very interesting and educational. Andy you mentioned that the development of this technology started from as early as the 1800s.[Unsuitable/Broken URL removed by Moderator] That’s quite interesting to know. Nevertheless you further stated that each attempt suffered the shortcoming of insufficient support. Probably, producers of these films should consider exploring themes and story lines that are a lot more captivating. In addition, a larger number of film producers worldwide should be encouraged to learn more about the technology and explore its possibilities in their work. If there are more 3D films out there, viewership will increase and more money can be harnessed.

  • Comment number 39.

    I wish to add my support fo continued and expanded 3D content on the BBC. I suspect there is not enough decent content available for a truely dedicated channel but I am content with having some 3D on the existing HD channel.
    As a non Sky user I found the recent tennis in 3D to be great. I am not a tennis fan but found the 3D to add considerably to my enjoyment, it brought the game to life for me.
    I am a user of the recent passive 3d TV technology and have been very satisfied, no headaches, no eye strain, low cost glasses including clip on. Personally I find 3D TV to be a better entertainment step in technology than HD was. The cost of sets whilst high, is not prohibitive any more. I hope some exposure by the BBC on non pay channels will encourage more users.
    Have one satisfied user BBC !!!!!

  • Comment number 40.

    These just huet my eyes looking through them, wondered if you can get perscription 3D glasses

  • Comment number 41.

    Dear Davey111 - thanks for the post. Only passive glasses I believe


  • Comment number 42.

    Andy thanks for this blog.

    I tried the Panasonic 3D system using shutter glasses and was blown away by the demo disc despite expecting to hate it!!

    The glasses were comfortable and light and the screen experience where most of the picture went back into the wall rather than out into the room was a great one.

    I think its worth mentioning here for those who don't like 3D that there's a vast difference between the difference systems and sometimes manufacturers as to the quality of picture achieved.

    Therefore you can't really judge 3D on one viewing of one technology or manufacturers system alone.

    I would assert that the best systems are now very good and well worth the money. However, 3D has some way to go in order to popularise itself and yet again we see the manufacturers being their own worst enemies just as we did with HD DVD and Blu Ray.

    These format wars really do no-one any favours and often kill technologies dead. Blu Ray still appears to me to have a slow take up despite the format war being over and I place that simply at tiredness amongst the public of these continual wars and uncertainty of which product to buy.

    If manufacturers really want technologies to take off including 3D, then they really need to test all the systems and get behind the best system as a whole in my opinion rather than trying to win market share for their own system while upsetting the public whilst doing so.

    I hope the BBC will persevere with 3D despite me being unable to view it!

  • Comment number 43.

    Dear Alsone thanks for the comments. And there's are more to come I'm afraid. It's not just the particular technology that makes a difference. Even with passive systems there is a big difference between glasses.

    Also - you may wear glasses for 2-3 hours watching a film but will you sit all evening watching 3D TV or will you expect to dip in and out?


  • Comment number 44.

    Each lens views only one of the overlapping images, and your brain puts the image together for a 3D effect. This type of television is also able to show 2D images.

  • Comment number 45.

    im just trying to work out how the bbc has money to throw at 3d when its trying to save cash, sure 3d is a nice technology and evntually will be great for documentrys and the like to showcase bbc talents.

    but with only a small number of households actually owning the equipment to make use of it, i just dont see the point if throwing a few million down the tubes in an effort to keep up with sky.

    and for anyone claiming the bbc need 3d to keep there current crop of production staff and not let them go elsewhere (sky) in short the bbc cant afford to keep them if they wish to go there as sky has a lot more cash to throw around at projects than the bbc will ever do sadly.


More from this blog...

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.