During World War II, he volunteered as an air raid warden, then spent the last two years in the British Army, based in the UK.
[1] In the late 1940s, McDermid had two bouts of tuberculosis, and in 1950 he moved to Stonehouse, hoping that the cleaner air there would improve his health.
He worked locally as a quantity surveyor, and became active in the Congregational Union of Scotland, serving on its building committee.
[1][2] In 1967, McDermid was elected to Hamilton District Council as an independent, but in 1970 he decided to join the Liberal Party.
He stood unsuccessfully for the party in Lanark at the October 1974 and 1979 general elections, and also in the high-profile 1978 Hamilton by-election, at which he took only 2.6% of the vote.