The Queen of England is having her two $14 million bespoke Bentley limousines converted to run on biofuels. Bentley will replace the 400 HP twin-turbo 6.75 liter V8 engines on the unique cars (above) by way of promoting the new range of eco-efficient models the famed marque plans to introduce by 2012, the London Daily Mail reports. The first of the Queen's one-off, supersized limousines, based on an ultra-luxe prototype and costing about $14 million to build, was a gift from Bentley on the occasion of her Golden Jubilee in 2002. Elizabeth II was so taken with it that she persuaded Bentley to build her another. "We have a lot of support from the Royal Family for our biofuel strategy," a Bentley exec tells the paper. "It is something about which they all take a keen interest." Prince Charles has already converted one of his Aston Martins to run on bio-ethanol made from surplus English wine, and has had his Jaguar, Audi and Range Rover converted to run on old cooking fat.