It was the moment royal watchers had been drooling over for months, a few seconds which not only provided visible hard evidence of a relationship they knew had been going strong behind the scenes, but also took a major gamble with the public's perceptions of the royal family.

To the whirr of 150 cameras, the Prince of Wales and his long-term companion Camilla Parker Bowles stepped out of the Ritz Hotel in London - and slid into the back seat of the waiting Vauxhall Omega. Not a Rolls-Royce, not a Bentley, not even a Jaguar. Just a normal - albeit top-of-the-range and chauffeur driven - executive saloon.

The Omega may well have been a step up for Mrs Parker Bowles, who arrived at the Ritz in a Ford Mondeo estate. But in the space of that single photo opportunity, the couple demonstrated once and for all the radical changes which have taken place in the House of Windsor. Meet the Vauxhall Monarchy - the downsized, environmentally-responsible, image-aware royal family for the 21st century It is still possible to remember a time when a leading royal would rather be caught in flagrante with his mistress than be seen around in a vehicle more popular with the managing directors of medium-size companies.

As a young bachelor, Charles developed a reputation as a man with a passion for the finer things in life - namely Aston Martins. He still has two, a DB6 and a Virage, but now they and the Range Rover he keeps for country jaunts have been joined by not one, but two Vauxhalls: the Omega of Camilla fame, and an estate used for carting his luggage and other necessities around. No doubt, that includes hanging a creased suit jacket inside one of the back doors.

Charles may have given an inkling of what was to come with his engagement present to Princess Diana, a Ford Escort, although she soon made up for that initial lapse by buying a convertible Audi.

But the monarchy and fine motoring go further back together than Charles and Diana. From the dawn of the motoring age, British royals have been keen to set the pace.

Back in 1897, Daimler became the first marque of car to convey the Prince of Wales when they were introduced to the future Edward VII by his friend and automobile fanatic, Lord Montagu of Beaulieu.

He must have been impressed: three years later, the prince bought one for himself, launching a trend which has seen more than 100 of the cars serve in the royal fleet.

These days of course, Daimler is part of the Ford's burgeoning stable, but the link with its past pedigree is sufficiently strong that the Queen still uses one. She also has four Rolls-Royce Phantom VIs, a Jaguar and three Rovers.

But there are already signs that the winds of change are also sweeping through Her Majesty's extensive garage. Last summer, Buckingham Palace announced that the time had come for some of its Daimler limousines to be replaced. The new recruits? Two Vauxhall Sintra people carriers, which will shortly be joined by a third.

The departure may not be as radical as it appears. The senior royals will stick to more opulent vehicles, while the Sintras will be used as the official means of transport for ladies-in-waiting and private secretaries.

But for royalist motoring traditionalists, this may be akin to the Queen decamping from Windsor Castle and moving into a semi-detached bungalow in Surbiton.

Before they get too sniffy, however, it is worth considering the reasons behind the change of policy.

'The Daimlers were getting old, and in time spares will be hard to come by and they will be expensive,' says a Palace spokesman. 'The people carriers have been converted to run on either unleaded petrol or liquid petroleum gas, and they can carry up to eight people, so they are an environmentally-friendly alternative.' But why Vauxhall? 'We worked out that of all the people carriers on the market, that was the one with the most British content. The alternatives were all either Japanese or American. Having sliding doors on both sides was also a factor.'

All very laudible, but undeniably dull. So as usual it is left to Prince Philip to prevent the Windsors from sinking into executive homogeneity. He recently took delivery of a new £30,000 version of his vehicle of choice for getting around London: a black Metrocab taxi.