Could the UK work with two different time zones?
Plans to change UK time to improve tourism have been floated but have prompted objections in Scotland. So why couldn't Scotland and the rest of the UK have different time zones? And what are the other logistical issues?
Moving the UK's clocks forward has always been controversial. Now the government's new tourism strategy, due out in the next few weeks, is expected to suggest just that.
It would see British Summer Time (BST) maintained during the winter months and "double summertime" applied during summer months, putting the UK one hour ahead of GMT during winter and two hours ahead during summer.
It would see clocks move forward by an hour from GMT in the winter and a further hour in the summer, to match Central European Time, meaning lighter nights but darker mornings.
MP Rebecca Harris is championing such changes in the Daylight Saving Bill in Parliament. She says the move would allow an extra 235 hours of daylight after work every year and deliver benefits including 100 fewer deaths from road crashes annually.
It would also purportedly save £200m a year for the NHS because of fewer accidents, boost British tourism revenue by £3.5bn and reduce carbon dioxide emissions through people leaving lights and heating off, it is claimed.
It's been debated repeatedly over the years and has even been tried twice, albeit temporarily. The clocks were moved forward by an hour during World War II, to maximise productivity at munitions factories and ensure people got home safely before the blackout.
It was again tried between 1968 and 1971. But after complaints in Scotland and northern England, MPs voted to end the experiment.
Distinguished advocates over the years have included Winston Churchill and today's supporters are many and varied, from the Football Association to Greenpeace.
But what are the logistical implications of changing the clocks?
The Scotland argument
For years the case in favour of changing the clocks has struggled because of Scotland. If it was introduced some of the northern-most areas would not see daylight until 10am during the winter months. Opponents argue this would increase accidents and make farmers' lives harder.
So could Scotland have a different time zone? It's been suggested several times over the years, but never been taken seriously. The list of objections include the havoc it would cause to travel timetables and the UK-wide TV schedule. And what if you worked in one nation and lived in the other?
But Russia and other large countries survive with multiple time zones. In the US some states operate on different times. The southern part of Idaho is an hour in front of the northern part. People learn to factor in the difference and eventually it becomes automatic. Travel timetables are always shown in local time and when meetings are arranged - for work or pleasure - people add "your time" or "my time" to clarify.
But UK Prime Minister David Cameron says he is determined to keep Britain a "united time zone". Alasdair Allan, SNP MSP for the Western Isles in Scotland, is also against the idea because it would alienate Scotland and make commutes across the border difficult.
Even those in favour of changing the clocks are against different time zones, arguing Scotland has the most to gain from change.
Dr Mayer Hillman, who has campaigned for daylight saving for the past 40 years, recently researched what the implications would be for Scotland for the Policy Studies Institute (PSI). He says Scotland would benefit more than the rest of the UK in terms of the economy. He estimates an extra £300m would be generated from tourism and 7,000 new jobs created.
The most serious criticism of changing the clocks is that darker mornings will mean more accidents, especially among children walking to school. When the change was made between 1968 and 1971 it did result in more deaths on the roads in the dark mornings, a fact that was widely reported.
But it was more than offset by a reduction of accidents in the evenings, something that has never been as widely reported. Overall there was a net fall in deaths and injuries on the roads, but many still perceive the clock change to be more dangerous.
"There were a lot of misconceptions about the success of the experiment at the time and they still persist," says a spokeswoman for the Royal Society for the Prevention of Accidents (RoSPA), which supports the move.
"But if you read through studies done back then they clearly show an overall decrease in deaths on the road. Studies since have also concluded the change would save lives and we agree."
A recent report by the Transport Research Laboratory - called Road Safety Beyond 2010 - suggests changing the clocks could reduce UK road deaths by 82 per year and serious injuries by about 212. It estimates that could save the government £1.4bn in terms of road safety benefits alone over 10 years.
Statistics also show there are over 50% more fatal and serious injuries on roads from November to February during peak afternoon times among adults, compared with the morning rush, says Dr Hillman. When it comes to children there are three times as many.
In the past farmers have been "fingered" as influential opponents of changing the clocks, says the National Farmers' Union (NFU). But it's not the case now. It takes a neutral stance to the proposals and says if anything, slightly more of its members are in favour of change.
"The NFU of England and Wales has no strong views on whether we should or should not put the clocks forward," says NFU director of policy Martin Haworth. "The last time we tested opinion among our members there was a narrow majority in favour of lighter evenings."
NFU Scotland takes a neutral stance too, but says there are concerns among rural communities about losing light in the mornings.
Significant changes in farming mean many of the arguments previously used are now redundant. Yes, dairy farmers still get up early to milk cows, but the animals are mostly kept indoors during winter and milked in artificially lit parlours. Daylight doesn't matter. Attitudes to changing the clocks largely depend on what people do on their farms, says the NFU.
"Whether extra daylight would be more beneficial in the morning or the evening depends very much on the work pattern on each individual farm," says Mr Haworth.
When it comes to tourism, there are strong arguments for changing the clocks. The extra hours of afternoon daylight will boost tourism revenue to the tune of £3.5bn in the UK and generate around 8,000 new jobs, according to a 2008 PSI report on the issue.
For companies dealing with clients abroad, moving in line with other European countries has obvious benefits. A report done by the Greater London Authority said changing the clocks would provide 40% more business time overlap with the continent for businesses in the City and enable people to attend morning meetings in Europe without staying overnight. This also applies to many businesses outside London.
"It's barmy that a great trading city like London is so out of kilter with the rest of Europe," says London Mayor Boris Johnson.
It would also provide more working time in the morning for trading with Asian markets.
But pushing the UK an hour eastwards would narrow the opportunity to speak to companies in the US, especially the West Coast, which would be nine or 10 hours behind the UK.
Much of Scotland's trade is also with Europe and is worth £15bn to the Scottish economy annually, says the PSI report on the implications for the nation. The time difference reduces efficiency for companies, it adds.
People don't like getting up in the dark
For many people it doesn't matter how many hours of extra daylight they get in the afternoon, it's the extra darkness in the morning that is the issue.
"You see it when the clocks change now, in the winter people think 'oh, God' and in the spring their mood is uplifted," says Dr Hillman. But he argues daylight hours in the morning are usually wasted anyway, because we aren't up or are just getting ready to go out. The extra daylight hours in the afternoon can be better used.
Mr Allan says he understands the motivations of campaigners who want to change the clocks, but it is massively unpopular in Scotland and a lot of that is down to waking up in the dark.
"I recognise many of the benefits, like boosting the tourist industry and it staying lighter longer in the day," he says. "But there just isn't an appetite for change in Scotland and much of that is because people don't like getting up in the dark on winter mornings. I have to listen to what constituents are saying to me."
And it's not just because humans are lazy, we're built that way. The sleep body clock is orientated towards daylight and sensitive to it, says Prof Jim Horne of the Sleep Research Centre at Loughborough University.
"Biologically we're designed to wake up with the sunrise. If we do, it resets the body clock, makes us more alert and happier. It's more of a struggle to wake up if it's dark. That has psychological implications, we are more gloomy."