The racist incidents that Tull faced while playing football made life difficult for both him and his team-mates, so in 1911 he was sold to Southern League side, Northampton Town. For the next three seasons Walter made 111 appearances for the Cobbler's.

"Tull has now settled in the half-line in a manner which now places him in the front rank of class players in this position" - Northampton Echo 1913