Diamond Jubilee: How do you host a military spectacular?
The Queen's Diamond Jubilee is being marked on Saturday with a flypast of over 80 aircraft and the marching of 2,500 troops. So how do you go about co-ordinating such a military extravaganza?
The air is filled with the stamp of hobnail boots landing on concrete on the command of a sergeant major. The rehearsal, overlooked by an audience of tourists, is in full swing.
Two days before the Armed Forces Muster at Windsor, members of the RAF Regiment, Coldstream Guards and Royal Navy are practising the guard of honour at London's Wellington Barracks, led by the Royal Marines Band.
And it appears that the drill is an art - especially when the three services have slightly different methods and levels of experience.
"It's getting everyone to that same standard that everything happens at the same time and you have one uniform body of men and women bang on time," Major Rolf Kurth explains.
To the untrained eye it already looks rather impressive, but a little work is needed on spacing and the delivery of commands to ensure there is no "ripple effect" of feet landing along the line.
Planning started 18 months ago when the Queen was asked whether a muster could be brought to her for the first time, says the man in charge, Air Vice-Marshal David Murray.
The troops will march past the Queen on Saturday in the Quadrangle of Windsor Castle, then pass crowds in the town before mustering in an arena before an audience of 3,800 royals, veterans and family members.
Space inside the castle's walls was chosen for the marchpast as it provided an intimate setting, bringing the troops within two to three metres of the Queen.
"The young men and women marching past can look the monarch in the eye and she can look them in the eye - it symbolises the closeness of the relationship between the armed forces and the Queen," AVM Murray explains.
The Armed Forces paying tribute to the monarch during a Jubilee year is an established tradition.
Similar events were held for Queen Victoria and King George V, in which Royal Navy fleet reviews took centre stage as it was then the largest service.
"The muster is an opportunity to show the monarch what they do and what they look like at that point in history," military historian Peter Craddick-Adams says.
In Tudor England, musters were periodic assessments of local militia to see if they were available to act as a defence force.
"Historically, heads of state would lead their armies into battle - the last was George II in 1743 - while members of the Royal Family throughout the generations have worn uniforms and gone to war," Mr Craddick-Adams says.
Troops now pledge allegiance to the Queen and wear her crown on their cap badges.
"The Queen's relationship with us is so strong, partly because her father was in the navy, she was in the army, her husband was in the navy, her son fought in the Falklands War and her grandson fought in Afghanistan. She knows what it's like to be from a military family," AVM Murray says.
'Whip into shape'
Once the location was set and the number of people who could be accommodated calculated, troops were chosen to take part. Two weeks before the muster they were given time to brush up on the drills they are all taught in basic training.
All of those involved are ordinary working personnel, many recently serving in Afghanistan. Some of the navy personnel were on HMS Liverpool during the Libya conflict.
"We whip them into shape because sailors don't march, they go to sea. It's not alien to them, but they need a bit more practice than most to get it up to scratch," the navy's parade tutor, Chief Petty Officer David Artyshore, says.
The thousands of troops will spend many hours cleaning their kit to ensure they look their absolute best.
"On the day when they stand in front of the Queen it is immense and they all grow a couple of inches. Every one of them is up for this. They are very proud to be doing this," CPO Artyshore says.
It is a similar process for the pilots in the flypast which will include helicopters, Lancasters and Spitfires, Hercules and Tornados, finishing with the Red Arrows. Some will form the shape of '60' and 'E II R' for a special tribute.
Fl Lt Matt Compton, who has 10 years' experience of flying the Hercules C-130J, explains: "There are a lot of aircraft in congested airspace so for us it's about maintaining our position, and ensuring you are in the right place at the right time."
Before attention turns to the skies there will be a drumhead service, speeches by the chief of the defence staff and the Queen and performances of new pieces of music written especially for the event.
And those are just the parts of the operation that the public can see, as AVM Murray explains.
"There's a huge amount of detail required to get everyone to the right place at the right time. Everything from making sure the coaches are in the right place with the troops, to car parking for guests, making sure there is food, drink and toilets, and seating plans to ensure everyone is happy.
"We're great planners, it's what the military do."
In the past, musters had clear political motives - a calling card to other nations that 'this is the latest technology from the largest navy in the world'.
But despite some foreign leaders potentially being present, this muster is very much for internal consumption, Mr Craddick-Adams explains.
"It has even changed in the last decade, since the Golden Jubilee - this has veterans and families invited, we had not invaded Iraq or Afghanistan then - so this is very much a 'thank you' to servicemen and their families, very much a two-way thing."
And for AVM Murray, it is all about the Queen.
"We are keen to give her a day she will enjoy. There are so many good activities going on as part of the Jubilee celebrations and this is something that only we, the military, can do."
The Armed Forces Muster will be broadcast on BBC1 at 10:30 BST on 19 May.