Technical details show how different the Bentleys are to standard cars. The Bentleys are 6.22 metres long, nearly a metre longer than a standard Bentley Arnage. At 3.84 metres, its wheelbase is 1.3 metres longer than that of an average family sized saloon. The engine drives a standard, four-speed GM 4L80-E gearbox, which directs power through up-rated driveshafts to the rear wheels.

Although they have a powerful engine, the Bentleys, like any other cars, are subject to normal speed restrictions. On processional occasions, they travel at around 9 miles per hour, and sometimes down to 3 miles per hour.

The rear doors are hinged at the back and are designed to allow The Queen to stand up straight before stepping down to the ground.

The rear seats are upholstered in Hield Lambswool Sateen cloth whilst all remaining upholstery is in light grey Connolly hide. Carpets are pale blue in the rear and dark blue in the front.

Visibility is important. For many people, a glimpse of a Royal car driving slowly by may be their only opportunity to see The Queen or a member of the Royal Family. The Bentleys are fitted with a removable exterior roof covering which exposes a clear inner lining, giving an all-round view of their Royal passengers.

There are other cars in addition to the Bentleys. A Rolls-Royce Phantom VI was presented to The Queen in 1978 for her Silver Jubilee by the Society of Motor Manufacturers and Traders.

The oldest car in the fleet is the Phantom IV, built in 1950, 5.76 litre with a straight eight engine and a Mulliner body. It was used by Princess Elizabeth and The Duke of Edinburgh. It features a straight eight engine and a Mulliner body. Despite its age, the car is in fine condition, and is still used for occasions such as Ascot.

There is also a 1987 Phantom VI.

All the cars have fittings for the shield bearing the Royal Coat of Arms and the Royal Standard. The Queen also has her own mascot for use on official cars.

Designed by the artist Edward Seago in the form of St George on a horse poised over a slain dragon, it is made of silver and can be transferred from car to car. The Duke of Edinburgh’s mascot, a heraldic lion wearing a crown, is adapted from his arms.

For her private use The Queen drives a Daimler Jaguar saloon or a Vauxhall estate. Like every other qualified driver, The Queen holds a driving licence.

The Duke of Edinburgh has a Discovery and, for short journeys round London, uses a Metrocab. The private cars are painted Edinburgh green.

A number of Royal Mews vehicles have now been converted to run on liquefied petroleum gas (LPG), a more environmentally friendly fuel than petrol or diesel. Converted vehicles include a Daimler and The Duke of Edinburgh’s Metrocab.

While Royal cars do not clock up vast distances on the road, they have travelled widely. Even if The Queen travels to an official engagement by train, helicopter or plane, she will generally travel by State car upon arrival in a new town; the car is driven to the location ahead of her arrival. For State visits, Royal cars and chauffeurs have travelled as far afield as Moscow.

Cars are kept in the Royal Mews in purpose-built garages. In charge of the fleet of cars is a team of eight chauffeurs, whose task is to drive members of the Royal Family, senior Royal Household employees, and official visitors from one place to another.

Despite their special form and purpose, in many ways Royal cars are just like any others. They are liable to the Congestion Charge, payable by all cars which drive within central London. They need road tax, regular MOTs and insurance. They must follow all the rules of the road. And even a special police escort can’t prevent The Queen’s car being held up in traffic from time to time.