Tyrwhitt took part in the Zeebrugge Raid and the Ostend Raid on the night of 23 April 1918, for which he was awarded the French Croix de Guerre on 23 July. At the end of the war he accepted the surrender of the German U-boats at Harwich. He was also promoted to rear admiral on 2 December 1919, and created a baronet of Terschelling and of Oxford on 13 December.