This was Commodore Henry Harwood's Force G flagship at the Battle of the River Plate in 1939 in which the German pocket battleship Admiral Graf Spee was so badly damaged by three British cruisers that it had to take refuge in Montevideo harbour and then scuttled to prevent its being interned or falling into British hands.
The Town of Ajax was incorporated in 1941 from a townsite that had built up around a newly opened munitions factory. The original streets were named after HMS Ajax personnel that were at that battle, the main street being Harwood Avenue.
The munitions factory and the associated tank and artillery proving grounds are long since gone and the town is now a bedroom community in the exurban Greater Toronto Area.
TRIVIA NOTE: Earlier in his career, the now successful novelist Clive Cussler was a Hollywood adman. He was one of the copywriters responsible for the Ajax White Knight commercial slogan, "It's stronger than dirt."