He began playing as a child for Thornbury Town, another of his father's former teams, and initially joined Bristol Rovers as an amateur in 1956, a move which mirrored his older brother David who had also joined Rovers from Thornbury but died in a bungalow fire in Olveston before making any League appearances.
After two years as an amateur, Hamilton became a part-time professional in January 1958, aged 17, and made his first team debut in the 1958–59 season.
He made eleven League appearances in his first three seasons as a paid player before finally becoming fully professional in December 1961 at the age of 21.
He had a brief loan spell at Exeter City during the 1967–68 season and spent a year with Newport County the following campaign, but his knee trouble forced him to retire from the professional game in 1969.
Ian was a member of Gloucestershire County Cricket Club and has travelled to see England play in locations including Australia, Barbados and South Africa.