He fought (and lost) as Conservative candidate for Walthamstow West in the 1955 general election, losing to the incumbent, leader of the Labour Party and former Prime Minister Clement Attlee. He also contested, and lost, the by-election in March 1956 after Attlee moved to the House of Lords as Earl Attlee. Hornby was finally elected Member of Parliament at the by-election in June 1956 for the safe Conservative seat of Tonbridge, although, against a local Labour politician and with the unpopular government of Anthony Eden, the Conservative majority was cut to barely 1,600 votes.