Thomas Derrick was born on 20 March 1914 in Adelaide. He was the eldest son of David Derrick, a labourer, and his wife Ada. The Derricks were not well off and Tom often walked barefoot to attend primary school. He left school at 14, by which time he had developed a keen interest in sports. During the depression he subsisted on the proceeds of odd jobs; fixing bicycles, selling newspapers and working in a bakery. In 1931 he travelled to Berri, on the Murray River, looking for work which he eventually found in a vineyard at Winkie. He remained there for the next nine years.

He married Beryl Violet Leslie in 1939 and enlisted in the Australian Imperial Force on 5 July 1940. Derrick embarked for the Middle East with the 2/48th Battalion and soon proved himself to be an excellent soldier, gaining promotion to corporal while his unit was in Tobruk. In July 1942 he was awarded the Distinguished Conduct Medal for his bravery and leadership at Tel el Eisa. At the end of that month Derrick was promoted to sergeant. By October his unit was in action at El Alamein, where he again served with distinction.

Derrick's unit returned to Australia in February 1943, training in north Queensland and Papua before helping to capture Lae in September. In November the 2/48th were in action at Sattelberg, overlooking Finschafen. Fighting amidst rugged terrain and under heavy fire from Japanese machine guns, Derrick performed the feat that earned him the Victoria Cross. Scaling steep cliffs, under fire, hurling grenades and using his rifle he cleared ten machine gun posts, making possible the capture of Sattelberg.

The 2/48th returned to Australia in February 1944 and in August Derrick was posted to an officer training unit. He was commissioned as a lieutenant in November. On 1 May 1945 he took part in the landing at Tarakan, Borneo. Later that month he led his platoon against a heavily defended position code-named Freda, gaining all but the highest knoll. That night a Japanese machine gun fired into the Australian lines. As he sat up to check that his men were all right, Derrick was hit by five bullets from the gun's second burst. He had been lightly wounded before, but recognised that this time his wounds were mortal. He died on 24 May 1945 and was buried in Labuan War Cemetery. A superb soldier, Derrick has also been described as a sensitive and reflective man - widely respected in the AIF he remains one of its better-known figures.