At 17 years and 256 days old, Allen's appearance for West Ham United against Arsenal in the 1980 FA Cup Final made him the youngest player to appear in an FA Cup final at Wembley Stadium, though James Prinsep played at a younger age at Kennington Oval in 1879.
He remained at White Hart Lane until 16 September 1993, when a £550,000 deal took him to Southampton.