Former film extra Knowles became secretary and manager of Tranmere Rovers in 1936. He masterminded Rovers’ triumphant championship season in 1937-38, when five points from their three final games clinched promotion from Division Three North to a first ever season in Division Two. It is still Rovers' sole championship in the Football League. However, they were relegated the next season having won just six of 42 matches – the all time worst record of any team in Division Two.
Knowles left the club in 1939, at the start of World War II.