The following are the outline details of the loss:

The sloop sailed from Milford Haven 14 December to carry out a patrol between the Tuskar Rock and the Smalls Lighthouse following several reports of submarine activity in the area. At 3.30pm on 15 December a submarine was sighted on the surface on the starboard bow, which dived as the sloop approached. Thirty minutes later she was struck by a torpedo on the port side abreast the after boiler room. The explosion killed several stokers and injured several others; the engines were put out of action and the boiler room started to fill with water. A periscope was briefly sighted astern and a depth charge was dropped, but to no obvious effect. The ship took a ten degree list to port but remained afloat. The US destroyer O'Brien (DD.51) closed and lifted off most of the crew, leaving the captain, Commander Charles Herbert Oxlade RNR and Lieutenant Charles Stewart RNR onboard. That complete, a tow was rigged and the O'Brien commenced towing the Arbutus until later that night the tugs Francis Bailey and Margaret Ham arrived to take over towing. At 02.55 the crews of the tugs heard an explosion and the Arbutus disappeared, the Margaret Ham having to hastily slip to tow to avoid being capsized as the sloop sank. A search revealed only a patch of wreckage. It was believed that she had been torpedoed for a second time. Her attacker had been the UB-65. The position was then 51.38N 05.24W. In all two officers and seven men lost their lives.

(info extracted from TNA ADM.137/3292)