Bentley as a marque started production in 1921 with the iconic 3 litre , and although successful at Le Mans and elsewhere they were underpowered compared to some alternatives on offer. A 6 cylinder version with a larger bore came next (the 6 1/2 litre and Speed 6 models), but there was still some demand for the old fashioned 4 cylinder , and the 3 litre was up rated with a bigger bore block to make the 4 1/2 litre. At the end of 1930 the 8 litre was finalised using the 110mm bore, to coincide with the Great Depression, and the irritation of Henry Royce, who did not appreciate the high quality home grown competitor. W.O. had little control of Bentley Motors since Barnato had controlling share, during which time Barnato won LeMans 3 times in the works team of Bentleys. Barnato had authorised the Blower Bentleys against WO's wishes, at much expense, and pushed through a costly 4 litre with engine designed by Ricardo to deal with the depressed markets. According to WO one of their big problems was that everything was bought out, and nothing made in house, but slowly they were getting to teh point that this was going to happen. An amicable sale was agreed to Napier but Barnato made sure Rolls Royce got the company. And WO was made to contractually work for Royce doing fairly menial testing work from 1932 to 1935, before he was able to leave, going to Lagonda.
The Rolls Royce built "Derby" Bentleys came on stream in 1933 as "The Silent Sportscar". This was a sporting version of the 20/25 Rolls Royce, and when the 25/30 was made the Bentley became the 4 1/4. Just before the war a new model, called the Mk5 was built, which was the basis for the post war Mk6. The Mk6 had increased capacity from 1951 which led onto the R Type in 1952. In 1955 the new S type series started with a 4.9 litre engine, and later on a V8 engine of 6.2 litres in the S2 and S3. This same engine made it's way into the T1 which now had an integral chassis with body, while for the T2 and Corniche the engine was eventually enlarged to 6.7 litres.