He studied medicine at St Mary's Hospital, London graduating with a 1st class degree in 1993. He then worked in the NHS before turning to a career in broadcasting.

His first job in television was for The Sky Travel Guide on Sky Travel giving health advice about holidays. This was followed by three years contributing to CBBC's programme Newsround, which led to Watchdog, Healthcheck, Tomorrow's World and others before Living's Most Haunted Live!, Five's The Wright Stuff and Richard & Judy.

He was the studio presenter on Most Haunted Live! for 41 shows from October 2002 to October 2005. In 2010, Bull made his American television debut as a contributor on the daytime talk show The Rachael Ray Show.

Bull has hosted sessions at the Conservative Party conferences, and taken part in other Conservative events. He has spoken out on sex education, saying that children must be given frank information on gay, as well as heterosexual, sex.[1]

On 16 December 2006 Bull was selected to represent the Parliamentary seat of Brighton Pavilion at the 2010 general election for the Conservative Party. He withdrew his candidacy in June 2009 to lead a Conservative Party policy review on sexual health with Anne Milton, the shadow health minister.

Bull is the author of two books.

Bull is also the co-founder and chairman of IncrediBull, a creative communications agency.

Bull is a celebrity ambassador for the British Red Cross and a Patron of the Cystic Fibrosis Trust, with whom he has been associated for more than a decade, as well as a spokesperson and proponent for cancer research and sexual health. He is also a supporter of The Duke of Edinburgh's Award and frequently works with young people in schools on behalf of the organisation.