The I Avon Trophy was a non-championship Grand Prix which was held at the Castle Combe Circuit on 1 October 1955, three weeks after the end of the season.

The race was won from pole by American, Harry Schell, ahead of privateer Horace Gould, in second and Bob Gerard in third.

The inaugural Avon Trophy, although post-season and non-championship, was attended by numerous championship contenders from the 1955 season, as well as some new faces ahead of 1956.

Among those who entered the race were American, Harry Schell, privateer Horace Gould and Frenchman, Louis Rosier.

Peter Collins and future championship runner-up, Tony Brooks also attended.