nominated to be returned to the Royal Navy in September, but remained with the 7th Escort Group. She spent September working up with her Royal Navy crew and rejoined the group in October, where she covered convoys between Britain and West Africa. On 15 September she picked up the survivors of the Norwegian motor tanker Vinga, which had been damaged in an enemy air attack. She carried out escort duties in November–December, before taking passage to Devonport to undergo repairs. The St Nazaire Raid Campbeltown began the Devonport repairs in January. During this time, she was selected for a special operation and was withdrawn from regular service for modifications. She was to be used in Operation Chariot, a planned assault operation on the docks at Saint-Nazaire. In 1942 the German battleship —anchored at Trondheim in Norway—was considered to present a grave threat to Atlantic convoys. Should Tirpitz enter the Atlantic, the Louis Joubert drydock at Saint-Nazaire—which had originally been built for the liner —was a vital target; it was the only German-held drydock on the European coast of the Atlantic that was large enough to service the battleship. If this drydock could be put out of action, any offensive sortie by Tirpitz into the Atlantic would be much more dangerous for the Kriegsmarine to carry out, making it less likely that they would risk deploying her. Operation Chariot was a plan to ram an explosive-laden warship into the dock gates. Accompanying her would be a number of small boats carrying British Commandos, who would destroy the dock's pumping and winding machinery and other infrastructure. The troops would then be evacuated by the small boats before the explosives in the ship detonated. A particular difficulty was that the dock was located several miles up the estuary of the Loire River. As an obsolescent destroyer, Campbeltown was considered to be expendable and was selected to be the ram-ship. She spent February undergoing modifications. These included removing her third and fourth funnels and having the remaining two funnels raked to simulate the structure and appearance of a German Raubvogel-class torpedo boat. A 12-pounder gun was installed forward and eight Oerlikon anti-aircraft cannon were mounted on the upper deck. Some extra armour was provided to protect the bridge structure, and unnecessary stores and equipment were removed to lighten the destroyer. An explosive charge consisting of 24 Mark VII depth charges—containing a total of of