'Trial' was a British naval undertaking to facilitate the passage of the JW.61 convoy via the Arctic route to ports in the northern part of the USSR and also to cover the ships of the RA.61 convoy returning from the USSR to the UK (20 October/10 November 1944).
The JW.61 convoy comprised 30 laden ships including two escort oilers and one rescue vessel, as well as six ex-US submarine chasers being transferred to the USSR, and had as its close escort Commander E. C. Hulton’s British 8th Escort Group (destroyer Walker, sloops Lapwing and Lark, and corvettes Camellia, Oxlip and Rhododendron), and from 22 October the more distant cover provided by the light anti-aircraft cruiser Dido and destroyers Obedient, Offa, Onslow, Opportune, Oribi and Orwell of the 17th Destroyer Flotilla. More distant support was provided to this important convoy by Vice Admiral F. H. G. Dalrymple-Hamilton’s escort carriers Nairana, Tracker and Vindex, themselves escorted by the frigates Byron, Conn, Deane, Fitzroy, Inglis, Lawson, Loring, Louis, Mounsey, Narborough, Redmill and Rupert of the British 15th and 21st Escort Groups.
The British were concerned that the Germans, after the damage which had been inflicted on their battleship Tirpitz on 15 September in 'Paravane', would make a greater U-boat effort than normal to inflict decisive damage on the JW.61 convoy, and it was for this reason that the normal close escort was supplemented by two rather than one support group as well as a third escort carrier to provide additional strength against German air and U-boat attack.
The combination of the anti-submarine escorts and carrierborne aircraft cleared all U-boats from the JW.61 convoy’s path, however, and all the ships safely reached the Kola inlet on 28 October.
Of the homebound RA.61 convoy’s 31 unladen ships, including two escort oilers and one rescue ship, some left from the White Sea on 30 October and the others from the Kola inlet on 2 November. All of the merchant ships reached Loch Ewe safely, but the frigate Mounsey suffered damage in an attack by Kapitänleutnant Günter Wieboldt’s U-295 on 2 November and had to turn back to the Kola inlet.