Leyton, London born left half Len Graham had started his football career with junior clubs Capworth in 1921 and Leytonstone in 1922, as well as touring with the Middlesex Wanderers, before joining Third Division (South) Millwall, initially as an amateur, turning professional in October 1923, where he developed into something of a stalwart for the club. He made his Football League debut at Brighton & Hove Albion in December 1923 and over the next eleven seasons he scored 8 goals in 341 appearances for The Lions, playing 34 times as Millwall won the Third Division (South) Championship in 1927-28, becoming club captain and playing his final game in October 1933 before his retirement due to injury.
He represented The Professionals in the 1925 FA Charity Shield match and also played for The Football League in a 4-3 win over The Scottish League at Goodison Park in March the same year, but the highlight of his career was winning two caps for England, the first against Wales in a 2-1 win at The Vetch Field in February 1925, the second in a 2-0 defeat to Scotland in April 1925 at Hampden Park. He was also a non playing reserve in March 1926 for England’s match against Wales at Selhurst Park. He also went on the FA Tour to Australia in 1925.
In 1935, he replaced Sydney Puddefoot as an FA instructor to Kent Secondary Schoolboys.
He also played county cricket for Essex in 1926, making two appearances for the county as a right-handed lower order batsman.