For conspicuous gallantry and devotion to duty while commanding a composite company of twenty Lewis guns. Under heavy enemy attacks his courage and cheerfulness inspired his men and caused them to hold on to a difficult position under very trying circumstances.[5]
In November 1918, with only a few days left in the war, Gatehouse was awarded a Bar to his MC. The Bar's citation stated the following:
For conspicuous gallantry in command of a company of fourteen tanks. He followed close behind, as they proceeded into action, under heavy shell and machine-gun fire, and superintended their movements in the clearing of two enemy positions. During this time he was knocked down by a shell bursting beside him. In two subsequent actions he again displayed great courage, and the success of these tanks was in great measure due to his skill and judgment.[6]
After the war Gatehouse transferred to the Royal Tank Corps (later the Royal Tank Regiment) in 1931.[2] He was appointed commandant of the Mechanisation Experimental Establishment at Farnborough in 1933.[2]