[1] He served as commanding officer of the submarine HMS Ambush in the Far East from 1964 to 1966.

In 1977 he was appointed commanding officer of the nuclear submarine HMS Churchill and also as Captain of the 3rd Submarine Squadron and in that role took part in the Queen's Silver Jubilee Fleet Review in June 1977.

[3] After that he became Captain of the Fleet, Home Fleet in October 1983, Chief of Staff Naval Home Command in December 1985 and Flag Officer Submarines in May 1987 before retiring in September 1989.

[5] Grenier is credited with having designed the 'dolphin badge' worn by qualified submariners in the Royal Navy.

[7][8] In 1957 Grenier married Jane Susan Bradshaw; they have two sons and one daughter.