'Trammel' was a British naval undertaking to lay a defensive deep-water minefield off the Kola inlet of the northern USSR to prevent U-boat attacks on the convoys entering or leaving the inlet, which is the main approach to Murmansk (17/26 April 1945).

The undertaking was the complement to 'Roundel' covering the JW.66 outbound convoy, and used the same ships to protect the RA.66 inbound convoy, initially by laying a defensive minefield and undertaking anti-submarine sweeps, and later by providing air cover. The cruiser minelayer Apollo and the minelaying destroyers Obedient, Opportune and Orwell, escorted by the light anti-aircraft cruiser Dido, departed Scapa Flow in the Orkney islands group on 17 April and reached the Kola inlet on 21 April. There they refuelled, and on the following day laid a field of 276 mines under cover of the 19^th Escort Group (frigates Anguilla, Cotton, Goodall, Loch Insh and Loch Shin), and the minelaying force then returned, reaching Scapa Flow on 26 April.