|Date of birth||April 27, 1971|
|Rugby union career|
Williamson started refereeing college games when he was 15, in 1986, before concentrating on playing the next year. After several seasons with the Paraparaumu senior side, Williamson went back to refereeing in 1997.
Williamson started his international career in 2010 refereeing Japan v Samoa in Tokyo. From 2011 onwards he was mainly an assistant referee, featuring in the 2012 June test series with Australia and Wales.