Mary and her husband had 2 sons who served and died on the HMS Exeter in WW2, a York Class Heavy Cruiser.

On 13 December 1939 the cruisers Exeter (8 inch gun), Ajax (6 inch guns) and Achilles (6 inch guns), on a raider-hunting mission in the South Atlantic, found their raider, the German Graf Spee. The German ship - commonly known as a "pocket battleship" for her 11 inch guns, but truly a specialized type of cruiser - should have been more than a match for the British ships. But in a pitched battle, the British managed to seriously damage Graf Spee while taking significant damage themselves. All three British ships were damaged, Exeter so severely that she had to turn away to make emergency repairs. During the battle, 72 British sailors were killed and 36 men killed from the Graf Spee.

Admiral Graf Spee also turned away from battle, fleeing at high speed for Montevideo, Uraguay, where she sought shelter to carry out her own repairs. The two remaining battle-worthy British ships blockaded the port, and the heavy cruiser HMS Cumberland raced up from the Falklands to replace the wrecked Exeter. Three days later, forced by international law to leave neutral Ugaguayan waters, and believing the British force to be much stronger than it was, Admiral Graf Spee blew herself up in the Rio de la Plata.

Exeter was soon repaired but was lost to the Japanese cruisers Myoko and Ashigara in the Java Sea on March 1, 1942. 54 were lost.

HMS Encounter was also sunk in the same battle.