[1] After serving a period as a geographer, Willis was elected to the New South Wales Legislative Assembly as the Liberal member for Earlwood in 1950.

[1] He received a Bachelor of Arts with double honours in Modern History and Geography (BA (Hons)) from Sydney University in 1942.

[10] During his time as member for Earlwood, Willis catered to the changing demographics of his electorate by creating the first-ever Greek branch of the Liberal Party and formed the first Young Liberals branch in Australia, which counted among its recruits future Prime Minister John Howard (1996–2007).

After retaining his seat again with 59.95%,[13] he was appointed to the post of Chief Secretary and Minister for Tourism by Premier Askin in May 1965 to June 1972.

From June 1972 to January 1976 he was Minister for Education, where he presided over a huge expansion of schools, teachers and ancillary staff.

For his service as Deputy Leader he was appointed a Knight Commander of the Order of the British Empire (KBE) on 14 June 1975.

At the party room meeting on 20 January 1976, parliamentary backbencher Neil Pickard called a spill motion which carried 22 votes to 11.

[17] Willis was then duly sworn in as Premier on 23 January, alongside his reconfigured Cabinet, by the Lieutenant Governor of New South Wales, Sir Laurence Street.

[17] His most significant decision was to set up in April 1976 the long-demanded inquiry into the prison system in the form of a Royal Commission under Justice Nagle.

Willis also introduced Daylight Saving time, to be decided upon in a referendum,[6] scrapped the unpopular petrol tax and announced a masterplan for Sydney's transport system.

[19] When former Minister Steve Mauger resigned on 27 January 1976, sparking a by-election in his seat of Monaro in May, and early polls had indicated a large swing to Labor, Willis announced an early election on 1 May, thereby cancelling the by-election in the hope of preventing a larger move of voters against the government.

I have experienced the pleasures of success and the frustrations of failures on a number of occasions...I leave the position of Leader of the Oppostition with no bitterness but naturally with a great amount of sadness" On 16 December, he formally resigned as leader at the party meeting and was replaced by Peter Coleman.

[22] On his retirement, he was permitted by Queen Elizabeth II, on the Governor's recommendation, to continue to use the title "The Honourable" for life.

[24][25] After retiring from politics Willis held positions with the Royal Australian College of Ophthalmologists and the Arthritis Foundation, of which he was executive director from 1984 to 1991.

[2] Willis left his residence in Bardwell Park and moved to Neutral Bay, where his marriage collapsed.