John represented Great Britain at the 1992 Barcelona Olympics and won a silver medal in the 4 x 100 metres relay at the 1993 World Championships (he ran in the heats and semis but not the final). He also won a silver medal at the 1996 European Indoor Championships and reached the final at the 1993 World Indoor Championships. In addition, he represented his country at two World Championships, in 1993 and 1995.