A by-election was held in the British House of Commons constituency of Epping Forest on 15 December 1988, following the death of Conservative Member of Parliament (MP) Sir John Biggs-Davison.

Thompson had been a founder member of the Social Democratic Party (SDP) and had served as a councillor in the local area since 1984.

His main campaign issues were saving a local hospital from closure and defending the green belt status of Epping Forest.

[2] The rump SDP, which had rejected the merger with the Liberal Party, also put forward a candidate, Michael Pettman.

Pettman, a solicitor and local councillor, had been the candidate for the SDP in Epping Forest at the 1983 general election.