The Bristol 403, in production from 1953 to 1955, was a development of the 401 with a more powerful (1971cc six-cylinder) engine, giving about 100 horsepower. Stability was improved thanks to a front anti-roll bar and the brakes were also more efficient thanks to Alfin drums. There was no shortage of owners of the 401 who mounted the updates of the 403 on their own. In total, the 403s built were 281.