Leaving school at the age of 16, he took up various jobs which included a period as a messenger at Parliament House.

[1] Upon the outbreak of the Second World War, Gratwick sought to join the Second Australian Imperial Force (AIF).

[1] Following completion of his training in July 1941, Gratwick embarked for Libya, where he was assigned to the 2/48th Battalion (a South Australian unit) with the rank of private.

Gratwick, realising the seriousness of the situation, charged a German machine-gun position by himself, and killed the crew with hand grenades.

In inflicting further casualties he was killed by machine-gun fire, but his brave and determined action, for which he would be awarded a posthumous Victoria Cross, enabled his company to capture the final objective.