The Royal car at the Royal Wedding

All eyes were on Prince William as he arrived at the Westminster Abbey, resplendent in a red tunic of the Irish Guards and accompanied by Prince Harry. But certainly there were a lot of eyes that were stuck on the Bentley State Limousine that carried the groom, one of the most exclusive cars by virtue of being the only one ever made.

Designed with inputs from the Queen herself, Prince Phillip and the head chauffeur, this bespoke limo ensures it's perfect for the Royal family's exacting standards.
Understandably, details of this one-off limo are scant. Three feet longer, 10 inches taller, and six inches wider than a standard Bentley Arnage, it is powered by a twin-turbocharged, 6.75-litre V8 Engine that has been modified from Bentley's Arnage R version to produce 400 hp (300 kW) and 616 lb•ft (835 N•m) of torque. Maximum speed is 130 mph (210 km/h). It is equipped with broad coach doors that open to the rear almost 90 degrees.
The car has been given armoured bodywork and glass, a mine-resistant floor, a cabin that can be sealed against a gas attack, and kevlar enforced tires. These security and safety measures raise the car's weight to almost 4,000 kg.
The only seat in the car that's leather is the driver's because the Queen and Prince Phillip prefer  lamb's wool covering on their seats. British textile manufacturer Hield Brothers produced the Lambswool Sateen cloth used for the upholstery of the rear seats.
Only two such cars were made, making it even rarer than the Rolls-Royce Phantom IV, of which just 18 were built for royalty and heads of state. You could have all the money in the world and Bentley wouldn't be swayed to build another.