As a player, 16 year-old Les Allen made his senior football debut in February 1953 for Briggs Sports in an unforgettable FA Amateur cup quarter final tie at Victoria Road, Dagenham against the holders Pegasus, the great amateur team of the 1950s, a match which the Dagenham works team won 3-0 with Les scoring one and making the other two. Les was an apprentice at Fords and eventually signed as an amateur for Chelsea in September 1954. He was an exciting centre-forward who scored 11 goals in 44 league appearances.
He joined Tottenham Hotspur in December 1959. He was a key member of Tottenham's double winning side of 1960-61, forming a lethal goalscoring partnership with Bobby Smith. He scored 47 league goals in 119 appearances, but struggled to retain his place following the arrival of Jimmy Greaves.
He joined Queens Park Rangers in July 1965 and scored 55 goals in 123 starts and five substitute appearances. He was a member of the Q.P.R. team who became the first Third Division side to win the League Cup.
He briefly managed QPR during the 1969/70 season. In November 1972 he became manager of Swindon Town, remaining in charge until 1974.