Pontypool, Monmouthshire born wing half William Robertson started his career as an inside forward but had more success after a switch to wing half. He began his football career with Abercarn in 1894 before joining First Division Small Heath (later Birmingham City), making his Football League debut against Blackburn Rovers in February 1896 scoring in a 2-1 victory, although Small Heath were relegated at the end of the season. He soon became a first team regular, missing only a small number of matches until he joined Southern League Bristol Rovers in 1899 after 15 goals in 103 appearances. According to the Bristol Mercury, writing when Robertson first joined Bristol Rovers in 1899 “Last season he was looked upon as the best half in the Small Heath team.”
He returned to Small Heath in 1902 but didn’t make any further first team appearances in 1902-03 before re-joining Bristol Rovers, with whom he finished his career.