The Admiralty continued full-scale and laboratory experiments after war began because much of the fleet still carried older protection and the new arrangement had not yet faced combat. Work at Cambridge and Portsmouth included a full-size battleship section fitted with the latest version of the system. The first wartime proof came when the Edgar-class cruiser HMS Grafton was torpedoed by a German submarine in June 1917. Her protection prevented destruction, allowed her to steam back to Malta, and spared the crew from injury. The hit provided the combat test the design team had lacked. Captain H. E. Grace, son of the cricketer W. G. Grace, then wrote personally to the Admiralty to praise the protection on behalf of himself and his crew.
Notable Point · 18:46-21:03
HMS Grafton validates torpedo-bulge protection
A 1917 U-boat torpedo hit on HMS Grafton provided wartime evidence that the new anti-torpedo arrangement could prevent a cruiser from being destroyed.