John began his career as a reporter on the Lincolnshire Echo before moving to BBC Radio Lincolnshire in 1982. His first job with network radio was in 1996 as a sports reporter for BBC Radio 2 and a news reporter for Radio 4 on the Today programme.

In 1998 he became presenter of Sport On 2, which he hosted for six years until the advent of Radio Five Live, when he moved to a daily news programme. During his radio career, he has presented five Olympic Games, several rugby and football World Cups, 19 Wimbledon Championships, 12 Open Golf Championships, and numerous other major sporting events. In 1997, he was named Broadcaster of the Year at the Sony Awards, and in 1998, Radio Personality of the Year by the Variety Club.

He hosted his own BBC One sports chat show Onside for seven series, and is a regular presenter on Grandstand and other sports programmes, including the daily highlights show from Wimbledon tennis championships.