 He won gold at the 1987 European Championships (Strasbourg) in the 100-metre butterfly, and was also part of the team which took silver in the 4×100-metre medley relay and going into the 1988 Summer Olympics in Seoul, South Korea, he was one of the pre-race favourites to win, having been undefeated for over two years in the 100-metre butterfly.He qualified fastest into the final, where he took bronze in a time of 53.30 seconds, breaking both the British and Commonwealth records in the process.Jameson retired from competitive swimming in 1989.