Let's face it: The Queen could use a new set of wheels. Now, there's nothing wrong with the Bentley State Limousine, which hasn't exactly led a hard life. But the car, created to celebrate the 50th anniversary of Her Majesty Queen Elizabeth II’s accession to the British throne, entered service way back in 2002. To put that in perspective, the car is older than Crocs, Gmail, The Da Vinci Code, and Top Gear with Jeremy, James and Richard.

Bentley's grand Mulsanne has been the State Limo's heir apparent since its 2010 debut, but although it certainly exceeded Royal specifications for bling, the car's rear-seat room was about a metre or so shy of "fit for a queen" status. Well, that changes with the debut of the Mulsanne Grand Limousine by Mulliner, unveiled today at the Geneva motor show. This privately commissioned (but eminently reproducible) car headlines a complete makeover of Bentley's flagship saloon.

The Grand Limousine adds a full metre to the Mulsanne's not-inconsiderable length, and raises the roofline by 79mm. The rear compartment features thronelike seating for four. Between the front and rear compartments, a pane of electrochromic privacy glass changes from transparent to opaque at the touch of a button.

The bigger news — figuratively, if not literally — is the revamped Mulsanne range, which includes the very nice standard-wheelbase and very fast Speed models, along with an entirely new Extended Wheelbase model, which adds 10 inches of rear-seat leg room. All three are are favoured with smart new front-end styling and a Bentayga-load of high-tech goodies — including a touch-screen infotainment interface and a 20-speaker, 2200-watt Naim audio system.

True to its name, the Mulsanne Extended Wheelbase offers an additional 250mm (9.9in) of rear-seat leg room, a wealth of space that can easily accommodate large dogs, small butlers or a modest production of Noël Coward's Private Lives. The two rear seats, essentially the world's nicest dentist chairs, feature power-deployable leg rests, ventilation and massage functions, privacy curtains and, overhead, a suitably vast glass roof. Rear-seaters also get the Bentayga's handy Bentley Entertainment Tablets, which emerge like slices of warm toast from the front seatbacks. Intended to take advantage of the car’s on-board 4G wi-fi system, these detachable Android devices feature 10.2in screens, an expandable 32 gigabytes of storage and front-facing cameras for the occasional Royal Selfie.

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