His three siblings all achieved success in their fields: his sister was Alison Patrick (1921–2009), an internationally known historian of the French Revolution; his brothers were David Hamer (1923–2002), a federal Liberal politician, and Alan, a Rhodes Scholar, chemist and managing director of ICI Australia.

He was a member, with his brother Alan, of the College First XVIII Australian Rules football team, and was Secretary of the Student Club.

He was commissioned as an officer in August 1940 in 2nd/43rd Battalion AIF and served at Tobruk, Syria, El Alamein, New Guinea and in Normandy.

Realizing that the Liberals had a year at most to retool their image before a statutory general election, Bolte retired in 1972 and endorsed Hamer as his successor.

Despite opposition from the conservative wing of the party, Bolte's support was enough for Hamer to prevail in the ensuing leadership ballot, and he was sworn in as premier on 23 August.

Hamer represented such a sharp change from the Bolte era that he was able to campaign in the 1973 election as a new, reformist leader, despite the fact that the Liberals had been in power for 18 years.

Employing the slogan "Hamer Makes It Happen", he won a landslide against the Labor opposition under Clyde Holding, increasing his party's already large majority.

Frank Wilkes had taken over as ALP leader from Holding in 1977, and took Labor into the 1979 election with a realistic chance of winning government for the first time since 1955.

It reformed the administration of the highly centralised Department of Education in Victoria into a regionalised organisation with devolution of greater control to local schools.

These changes were not enough to prevent Labor from taking seven seats off the Coalition in Victoria at the 1980 federal election, over half of its nationwide 12-seat swing.

He died of heart failure in his sleep on 23 March 2004, and his family accepted the offer of a state funeral from the Labor Premier, Steve Bracks.

[9] In March 2024, his 31-year-old grand-niece Amelia Hamer was selected as the Liberal candidate for the Division of Kooyong in the 2025 Australian federal election.