In early 1942, the German battleship Tirpitz had been active against the Arctic Convoys but it was feared that she might move south to attack shipping in the mid-Atlantic. The only dock on the French coast large enough to take her was at St Nazaire at the mouth of the Loire in south-east Brittany and Operation Chariot was planned to destroy the dock, thus effectively confining Tirpitz to northern waters.

On 26 March 1942, a small naval force left Falmouth consisting of HMS Campbeltown, an obsolescent destroyer packed with explosives, two escorting destroyers, sixteen motor launches carrying over 600 Commandos, Motor Torpedo Boat 74, and Motor Gun Boat 314 with William as part of the crew.

On reaching St Nazaire, MGB 314 guided Campbeltown to the target and successfully rammed the dock gate where she stuck fast, and two days later, she exploded, putting the dock out of use for the rest of the war. The plan called for the Commandos to destroy port facilities and then board the launches to return to Falmouth with the MGB providing covering fire.

However, the strength of German resistance prevented them from reaching the planned embarkation point, resulting in many casualties. Meanwhile, the MGB was being heavily attacked by ships in the estuary, as well as shore-based artillery, with William returning fire until he was killed.

He was buried in the Town Cemetery in Falmouth and later that year, William was awarded a posthumous Victoria Cross with the Citation reading:

The London Gazette of 19 May 1942 “For great gallantry, skill, and devotion to duty as gunlayer of the pom-pom in a motor gun boat in the St. Nazaire raid. Completely exposed, and under heavy fire he engaged positions ashore with cool and steady accuracy. On the way out of the harbour he kept up the same vigorous and accurate fire against the attacking ships until he was killed at his gun. This Victoria Cross is awarded in recognition not only of the gallantry and devotion to duty of Able Seaman Savage but also of the valour shown by many others, unnamed, in Motor Launches, Motor Gun Boats, and Motor Torpedo Boats, who gallantly carried out their duty in entirely exposed positions against Enemy fire at very close range.“