She was given the pennant number K310 and departed Boston the following month, bound via New York, for the Royal Naval Dockyard in the British Imperial fortress colony of Bermuda to conduct her "working up.

"[1] Allocated to the 44th Escort Group, part of the Western Approaches Command, Bayntun and her sister ship Bazely sailed on 2 April 1943 for Chesapeake Bay where they were to load stores for transportation to the United Kingdom.

However, Bayntun returned to Bermuda to pick up men from her crew who had been quarantined there due to scarlet fever before she sailed for England and ultimately got underway on 15 April for the British Isles, in company with Berry.

He was allocated as an additional escort to this group for the outward passage, with instructions to proceed to Boston on completion, to have new bearings fitted to the diesel engines, as they were badly worn.

[3] In September, an accident in Bayntun's forward motor room caused extensive damage and flooding, and the resultant repairs kept her in the yard at Belfast until 6 December.

Bayntun located the U-boat in the fading daylight and carried out three attacks, joined by the Canadian corvette HMCS Camrose which made five.

Bayntun remained in port for voyage repairs and enjoyed a brief respite from convoy duty before heading back to Gibraltar on 13 February.

On 1 September, Bayntun took part in the hunt for the killer of Hurst Castle, a corvette that had been torpedoed 11 miles (18 km) north of Tory Island, but the search yielded no result.

Sailing for Scapa Flow in late January, Bayntun teamed with the frigates Braithwaite and Loch Eck on 3 February and sank U-327.

[1] Joining the Portsmouth patrol on 11 March, Bayntun made contact with a U-boat 10 days later, but the ensuing attack was not successful.