Cumberland was an associate of Dove-Myer Robinson and were both members of the Drainage League that opposed the Brown's Bay scheme supported by the then mayorJohn Allum. Later, he was elected to the Auckland City Council in 1953 as part of Robinson's United Independents ticket. He was re-elected in both 1956 and 1959; in the latter he was on the "Civic Reform" ticket that briefly succeeded the United Independents. He was the leader of the Civic Reform group at the 1959 election.