Thomson had been a successful keeper in Scotland before moving South. Impressive performances encouraged Aberdare and then Brentford to sign him, being a regular at both clubs (during his season at Griffin Park, he only missed 2 games). In his 18 months at Plymouth, he played 7 times before signing for City. City's reserve keeper Stanford was injured and Thomson was signed as cover for Jimmy Newton, who himself received an injury.

Thomson played 3 consecutive games, conceding 11 goals, including 7 on his debut in the humiliating drubbing by Walsall. Newton regained his place and Thomson moved to the USA to experience football in their new league.