On August 8, 1917, 130 miles southwest of Ushant? in the [Bay of Biscay]?, disguised as the collier Boverton and commanded by Captain Gordon Campbell V.C., Dunraven spotted UC-71?, commanded by Oberleutnant zur See Reinhold Saltzwedel. Saltzwedel believed the disguised ship was a merchant vessel. The U-boat submerged and closed with Dunraven before surfacing astern at 11:43am and opening fire at long range. Dunraven made smoke and sent off a panic party (a small number of men who "abandon ship" during an attack to continue the impersonation of a merchant).
Shells began hitting Dunraven, detonating her depth charges and setting her stern afire. Her crew remained hidden letting the fires burn. Then a 4-inch gun and crew were blown away revealing Dunraven's identity as a warship, and UC-71 submerged. A second "panic party" abandoned ship. Dunraven was hit by a torpedo. A third "panic party" went over the side, leaving only two guns manned. UC-71 surfaced, shelled Dunraven and again submerged. Campbell replied with two torpedoes that missed, and around 3pm, the undamaged U-boat left that area. Only one of Dunraven's crew was killed, but the Q-Ship was sinking.
British destroyer [HMS Christopher]? picked up Dunraven's survivors and took her in tow for Plymouth?, but Dunraven sank at 1:30am early on August 10, 1917 to the north of Ushant. Two [Victoria Crosses]? were awarded by ballot, one to the ship's First Lieutenant, Lt. Charles George Bonner RNR, and the other to a 4-inch gunlayer, Petty Officer Ernest Herbert Pitcher.
Captain Campbell later wrote:
Captain Campbell had been previously awarded the Victoria Cross, in February 1917, for the sinking of U-83?.