Taylor Gardner-Hickman netted the only goal as Birmingham stretched their lead at the top of League One to a commanding 12 points with a 1-0 win over second-placed Wycombe.
Birmingham extended their unbeaten league run to 18 games against a Wycombe side who were reduced to 10 men before half-time.
Gardner-Hickman scored his first goal for the club on Tuesday against Leyton Orient and followed it up by giving Birmingham the lead after 21 minutes at St Andrew’s.
Ryan Allsop’s long kick was collected by Gardner-Hickman, who took the ball on his chest before turning and volleying it.
Wycombe goalkeeper Will Norris produced an excellent save but, as he parried the ball, it spun back and bounced over the line.
Wycombe created chances to equalise but had midfielder Xavier Simons sent off in first-half stoppage time.
Simons went for the ball with Ethan Laird and brought the Birmingham right-back down with a lunging challenge. Referee Ben Toner gave Simons a straight red, deeming the tackle to be dangerous play.
Birmingham held on to take the three points and strengthen their firm grip on the promotion race.
