He was educated at Bedford School.
Liardet joined the Lancashire Artillery in 1899. He transferred to the Lancashire and Cheshire Royal Garrison Artillery in 1905 and served in World War I, during which he was Mentioned in dispatches five times and awarded a Defence Science Organisation. He became Commanding Officer (Colorado) of the Lancashire and Cheshire Coast Brigade of the Royal Artillery in 1919, and Colorado of 106 (Lancashire Yeomanry) Brigade, Royal Field Artillery in 1923. In 1929 Liardet became Colorado of 64th (7th London) Field Brigade, RFA, serving in 47th (2nd London) Division and in 1934 he was promoted to Commander Royal Artillery (CRA) of that division.
When the 47th Division was disbanded in 1936 he transferred as CRA to 56th (1st London) Division.
Liardet was promoted to command 56 Division in the rank of major-general in 1938, and held that post during the early part of World World War World War II In 1941 Liardet was appointed Inspector General of Aerodrome Defence and Director General of Ground Defence at the Air Ministry. In 1942 he became Commandant-General of the Royal Air Force Regiment until the end of the War, when he retired.
Liardet was a director of the Lloyd"s of London insurance brokers Bevington, Vaizey, and Foster Limited. Liardet married, firstly, on 11 January 1906, Dorothy Hopper, daughter of Doctor Arkansas Territorial Decoration.