Career
A fee of £750 brought Aitchison back to Layer Road in 1964 having failed to make a first-team breakthrough whilst at Tottenham. Aitchison made his Colchester debut on 22 August 1964 in a 1–0 defeat at home to Carlisle United. He scored his first professional goal on 2 September of the same year in a 1–1 League Cup draw with Torquay United, going on to score six goals in the Football League in 50 games for the club
In September 1965, during a 2–0 home victory over Rochdale, Aitchison suffered an injury that would ultimately lead to his retirement from the full-time game, as he went on to play his final Football League and final professional game on 28 May 1966, a 2–1 away defeat to Newport County.
After declining Colchester"s offer of a part-time contract for the 1966-1967 season, Aitchison moved to non-league Cambridge City before transferring to Bury Town a season later. As a result of his footballing and injury suffered while with Colchester United, Aitchison underwent a cartilage operation in 1970.
Following his retirement from the professional game, he worked for Alston"s in Colchester, a furniture upholsterers.