Arthur Laurence Rook was born in Bingham, England, and attended Oakham School and Brackley College. He initially served with the Maritime Artillery, providing gunners for merchant ships. When the regiment was disbanded in 1942, he joined the Royal Horse Guards and served in Egypt and Italy, earning a Military Cross in 1944.

At the 1952 Olympics, Major Laurence Rook did not finish the three-day event. However, the following year, he won gold medals in both the individual and team events at the European Championships. After retiring from the Army in 1954, he farmed in Sussex and later in Gloucestershire, actively participating in the administration of equestrian sports.

During his second Olympic appearance in 1956, Rook placed sixth in the individual competition and was the second-highest scoring member of the British team, which won gold in the three-day event.