The Bentley 6½ Litre and the high-performance Bentley Speed Six were rolling chassis produced by Bentley from 1926 to 1930. The Speed Six, introduced in 1928, became the most successful racing Bentley.
Two Bentley Speed Sixes chassis became known as the Blue Train Bentleys after their owner Woolf Barnato in March 1930 "raced" the French Blue Train which departed Cannes at 17:45 and, after a stop in Paris, was scheduled to arrive in Calais at 15:24 when Barnato already was in his club in London.
Background
By 1924 Bentley had been in business for five years. He decided to build a larger chassis than the 3 Litre, with a smoother, more powerful, engine. The new chassis would be more suitable for the large and heavy limousine bodies that many of his customers were then putting on his sports car chassis. The resulting car would be more refined and better suited for comfortable general motoring.
Prototype race
Bentley built a development mule with a 4¼-litre straight-six engine derived from the 3 Litre's four-cylinder engine. To disguise the car's origin, it had a large, wedge-shaped radiator and was registered as a "Sun". The chassis was given a large very lightweight