In late November 1940, Becher transferred to the recently launched destroyer as part of the ship's commissioning crew. While completing working-up exercises, "Napier" was tasked with transferring British Prime Minister Winston Churchill and his wife from Thurso in Scotland to the battleship , and later returning them to the mainland. With her working-up complete, "Napier" was initially posted to convoy duties in the North Atlantic, before setting sail in April 1941 with for the Mediterranean Sea. Arriving in May, she formed up as part of the Mediterranean Fleet.