Hawker was educated at Geelong Grammar School, and Trinity College, Cambridge, earning Bachelor and Master of Arts degrees in 1919 and 1922, respectively.

He saw action on the Western Front in the Ypres salient, and was injured on 11 August and again in the Battle of Loos on 25 September, resulting in the loss of his eye.

However, after a series of operations and rehabilitation, he was able to walk with two sticks, although his legs remained in surgical irons for the rest of his life.

Hawker joined the state council of the Returned Sailors' and Soldiers' Imperial League of Australia in 1921 and served as its vice-president.

On 23 September 1932, he resigned from the ministry in protest at its refusal to reduce parliamentary salaries in response to the Great Depression, having crossed the floor to vote as a minority in a controversial day in Parliament, and did not serve as a minister again, although he continued to represent the people of Wakefield as their elected representative.