[1] His family lived in Ponsonby, and he was educated at Mt Albert Grammar School, where he started his rugby career.

[3][4] Williams' international rugby career lasted from 1970 to 1978 in which he played 113 matches (including 38 international Tests) and scored 66 tries in all matches as an All Black (ten tries in Tests), which was a record until beaten by John Kirwan.

[6] In the 1983 Queen's Birthday Honours, Williams was appointed a Member of the Order of the British Empire (MBE), for services to rugby.

[7] In the 2013 Queen's Birthday Honours, Williams was appointed a Companion of the New Zealand Order of Merit (CNZM), also for services to rugby.

[8] He was promoted to Knight Companion of the same order in the 2018 New Year Honours (KNZM), for services to rugby.