At the end of the 1953 NSWRFL season Hammerton played in the grand final at hooker for South Sydney, scoring a try in their victory over St. George. In season 1954 Hammerton played in the grand final at hooker for South Sydney who defeated Newtown. At the end of the 1955 NSWRFL season Hammerton played in the grand final at hooker for South Sydney who again defeated Newtown. South Sydney came within one match of the 1957 NSWRFL season's grand final, however Hammerton was dropped from the team for the qualifier in favour of 22-year-old Brian Murray. Souths lost the match. The following season was Hammerton's last in first grade.
Hammerton was appointed a New South Wales selector in the 1970 pre-season. In 1972 Hammerton, who was already a New South Wales selector, won a position on the Australian Rugby League selection committee. A decade later he was still a national selector. He was replaced as chairman of Australian selectors by Don Furner in the 1989 pre-season.