Coach doors at the rear open to nearly 90 degrees. The cabin is armoured, blast-resistant and can be sealed airtight, and the tyres are reinforced with Kevlar.
The Bentley is used exclusively for official engagements. It has a mount on its roof for an illuminated crest and carries the Queen's mascot, depicting St George slaying the dragon.
The limousine was gifted by a Bentley-led consortium and was a public relations coup for the time.
The royal family have long favoured Rolls-Royces. At the time of Elizabeth II's accession, Daimler was the official marque for the family, but from 1952 there was an aggressive shift towards Rolls-Royce, which was granted a royal warrant in 1955.
Rolls-Royce and Bentley were part of the same group from 1931 until 1998, when Rolls-Royce Motors was sold to Volkswagen after a bidding war with BMW.
However, although VW had acquired the historic Crewe factory, the rights to the grille shape and the Spirit of Ecstasy mascot, it found it did not own the Rolls-Royce name and official logo - which were still the property of aero-engine company Rolls-Royce.
The name and logo were promptly licensed to business partner BMW, which then had the upper hand as it was already supplying engines to Rolls-Royce Motors and could withdraw them at a year's notice.
A deal was struck: from 1998 until the end of 2002, VW could build Rolls-Royces with BMW engines. From January 2003, BMW would assume exclusive rights to Rolls-Royce and VW could build only Bentleys.
It's no coincidence, surely, that VW-controlled Bentley secured No1 status for its brand as the deal with BMW drew to a close - ousting the custom-built Silver Jubilee Rolls-Royce Phantom VI (1977) from top spot.
The Queen might have been more interested in what was under the bonnet than which company owned which brand because during World War II, as Princess Elizabeth, she trained and became a fully qualified mechanic.
In 2009, a survey undertaken by the Automotive Technician Accreditation scheme in Britain asked consumers who they would be most grateful to see in a passing motorcade if their car broke down. The winner was the Queen.
