At this distance, no one can now quite remember how the Duke of Edinburgh agreed to become patron of the Caravan Club. President of the British Irate Motorists’ Society would have been more his thing.

To give him his due, he has been a loyal figurehead to the towing classes since 1952. His wife had just become Queen, caravanning was a bit of an elitist adventure – given the scarcity of car owners – and he was expanding his portfolio of good works to show that he was a proper royal and not just an early-retired sailor.

Yesterday was payback time. To mark the centenary of the Caravan Club he hosted a garden party at Buckingham Palace for 7,500 caravanners, all of whom were urged to leave their rigs behind and approach by public transport.

The burning question was: had the Duke, in all his 86 years, ever spent a night in a caravan? “He refuses to say,” a Palace spokeswoman said.

It is thought to be highly unlikely, given the static and spacious holiday facilities of Balmoral and Sandringham, but Trevor Watson, head of the Caravan Club, insisted that it was at least possible. “He likes carriage driving, which takes place in estates all over the country; people need places where they can get changed and have a cup of tea. They rely on caravans because of where they are.”

Fair enough, Mr Watson, but it’s not quite the same as hitching up the Swallow to the Escort and driving the wife and kids to two weeks of the simple life in Prestatyn.

But the Duke is not entirely ignorant of caravans. In 1987 he opened a Caravan Club site in the grounds of Sandringham, and in 1955 he and the Queen were presented with a half-size, fully equipped caravan, including a non-functioning gas cooking hob – for their children to play in. Twenty years later it was handed over to the Princess Royal for her children to play in, although they were said to be more interested in horses.

The Royal Caravan now lives in the Buckingham Palace Mews, and was wheeled out into the Quadrangle yesterday for the delectation of guests. Parked next to it was a caravan built in 1885 for the man whose fault it all is.

Dr William Gordon-Stables, a retired Royal Navy surgeon, passed by a group of Romanies one day and took a fancy to their freewheeling lifestyle. He ordered the world’s first leisure caravan – mahogany-panelled and drawn by four horses – from a maker of railway wagons in Bristol, and toured the length and breadth of the country in it, sticking, no doubt, to the inside lane, that being the only lane there was in pre-motoring days.

The third caravan on display was the winning entry in a Caravan Club competition to design the vehicle of the future. A blue and silver bubble, its prime characteristic was a roof formed of a single solar panel, to provide the power of self-sufficiency and perfect greenness. Palace garden parties don’t do bottled gas stoves, Melamine plates or folding picnic tables. But the grounds do have a superior toilet block hidden in the bushes which would do credit to one of the Caravan Club’s 200 official sites. And yesterday afternoon it was also able to provide one essential caravan ingredient: rain.

The whereabouts of our leading caravanista, Margaret Beckett, was not immediately clear. Slightly well-known enthusiasts who did attend, however, included Cheryl Baker, the former Buck’s Fizz singer, the actress Linda Robson, of Birds of a Feather, and Jamie Baulch, the Olympic athlete.

Guests were selected by ballot from the Caravan Club’s 1 million members, a figure that is growing by more than 10,000 a year. Nick Lomas, its spokesman, said: “Caravanning has enjoyed a resurgence since 2000. There has been a significant rise in motorhome touring in the UK as people seek a simpler and more nostalgic holiday.”

Prince Philip enjoys simple and nostalgic holidays, mainly shooting birds. But he prefers to base himself in a solid granite castle on Deeside, with electricity, running water, inside lavatory and a proper slate roof that dulls the noise of the drumming rain.

All aboard

— Number of caravan and motorhome owners: 1.7 million and growing

— Permission to tow: normal driving licence sufficient, but the Caravan Club offers manoeuvrability lessons

— Cost: from £3,000 for a decent trailer tent to £181,196 for a top-of-the-range 36ft Winnebago, built on a Mercedes chassis. Average towing caravan: £13,000.

— Customised motorhomes: up to £400,000

— Best towing car, 2007: Volvo V50

— Sites: 200 main Caravan Club sites throughout Britain, plus a further 2,500 certified sites taking up to five vans

— Most popular British site: Incleboro Fields, near Cromer, Norfolk, covering 21 acres

Source: Caravan Club