Admiral Martin Dunbar-Nasmith, who had been Commander-in-Chief, Plymouth, also took over responsibility for the Western Approaches from the start of World War II.

[2] On 7 February 1941, the headquarters was established at Derby House, Liverpool,[2] with a secondary control bunker built in Magee College, Derry.

Horton used the increasing number of escorts that were available to the command to organize "support groups" that were used to reinforce convoys that came under attack.

This freedom gave them much greater tactical flexibility, allowing the support groups to detach ships to hunt submarines spotted by reconnaissance or picked up by high-frequency direction finding (HF/DF).

In situations where the regular escorts would have had to return to their convoy, the support groups were able to persist in hunting a submarine for many hours until it was forced to the surface.