Promoted to Sergeant prior to embarking for Europe during WWI.

Tompkins set up a law firm with Cecil Barry Wake, Tompkins and Wake, in Hamilton in 1922.

Married Marjorie Rees Manning, the daughter of the then managing director of the Waikato Times, Arthur Edward Manning, in 1926.

He continued to serve with the Territorials, rising to the rank of 2nd Lieutenant in 1925.

During 1940-41, he served with a Home Service Battery, Royal New Zealnd Artillery, with the rank of Major. He attempted to go overseas, but he was not deemed medically fit enough for overseas service.

He served as president of the Hamilton District Law Society and was a member of the New Zealand Law Society Council, 1940-42.

He was elected a Hamilton City Councillor in 1955 and served until 1958.

Admitted to the Inner Bar as Queens Counsel, 1958. First barrister to achieve this status outside of Auckland and Wellington.

President of Birthright Hamilton, 1958-61.

Founding Trustee and president, in 1961-62, of the Waikato Savings Bank.

Chairman of Bartholomew Timbers Ltd, 1938-1963.

Member of the Board of Governors of the Waikato Diocesan School for Girls, 1934-1963.

Appointed Supreme Court judge, 2 August 1963.

Retired in February 1969.

Served as a judge of the Fiji Court of Appeal and chairman of the Legal Aid Authority.

President and life member of the Hamilton Golf Club.

Tompkins' surname is misspelled as "Tomkins" in the WWI Nominal Rolls. AWMM