The 'Derby Bentleys' began with the presentation in September 1933 of the Bentley 3.5-litre, although this was a 3,669cc version of the 6-cylinder engine already fitted in the Rolls-Royce 20/25. Bentley retained their sporting image by getting higher compression, twin carbs, a better camshaft and crossflow head to give about 110bhp. Many of the bodies fitted to these 'Derby Bentleys' were very heavy, so the car was upgraded with an engine bored out to 4,257cc to become the 4.25-litre Bentley in 1936, and sales of the 3.5-litre declined thereafter; 1,177 were produced.