Career
Born in Glasgow, McLennan worked as an engineering draughtsperson before taking on various full-time posts within the CPGB. He contested the Glasgow Govan constituency in the 1959 United Kingdom general election, then the West Lothian by-election, 1962. Govan in the 1966 United Kingdom general election. He became the National Organiser of the CPGB in 1966, and while holding this post, contested elections in Street Pancras North in the 1970 and February 1974 general elections.
In 1975, McLennan was elected General Secretary of the CPGB. He held the post while the party was in terminal decline, with factional fighting within the CPGB, finally stepping down in 1989.
After the dissolution of the party, in 1991, he joined the Communist Party of Scotland.