Kenneth John Campbell was born in Crofton Park, south London. The son of a Lloyd's insurance man, he was educated at St Dunstan's school, Lewisham. He was then articled to his uncle's architectural partnership, continuing to study for his RIBA finals at Regent Street Polytechnic. In 1933, he married Frances Almond, and joined the architect's department of the Miners' Welfare Commission. By 1938, he was responsible for the Miner's Welfare West Midlands sector - and had joined the Communist Party.

Campbell signed up for war service but was allocated back to the Miners' Welfare Commission, and was involved in designing the first pithead baths. For the period of the Blitz, he was seconded to the City of London on air-raid shelter design. In 1943, he began work on planning for London.

In the mid-1950s, Campbell was shortlisted for the job of chief housing architect for the London County Council. But the chair of the finance committee, having been alerted to his politics, opposed Campbell's candidature. Going further than that, a postive embargo was put on any further promotion. Campbell became overall housing architect to the London County Council and its successor, the Greater London Council, in all from 1960 to 1974.

For 22 years he was a member of the RIBA council, and vice-president from 1975 to 1977. He was chair of the board of architectural education, and president of the Association of Building Technicians. A member of the faculty of the British School at Rome, he was also consultant to the Coin Street development at Waterloo.