The Bentley 6½ Litre and the high-performance Bentley Speed Six were rolling chassis in production from 1926 to 1930. The Speed Six, introduced in 1928, became the most successful racing Bentley. Two Bentley Speed Sixes became known as the Blue Train Bentleys after their owner Woolf Barnato raced the Blue Train in 1930.

Joel Woolf Barnato was a British financier and racing driver, one of the "Bentley Boys" of the 1920s. He achieved three consecutive wins out of three entries in the 24 Hours of Le Mans race.