Birmingham sent a statement to their Sky Bet League One promotion rivals after coming from two goals down to beat Peterborough 3-2 and reclaim top spot.
Posh looked set to inflict a first league defeat of the season on the big-spending Blues after scoring twice in the opening 16 minutes through Ricky-Jade Jones and Emmanuel Fernandez.
However, the hosts hit back to level just after half-time before captain Krystian Bielik headed home what would prove to be the winner midway through the second half.
The visitors took the lead after just four minutes when Birmingham goalkeeper Bailey Peacock-Farrell was caught in possession on his goal line, allowing Jones to open the scoring with a simple finish.
The hosts had improved after going behind but Peterborough doubled their lead when Fernandez rose highest from a corner to head the ball past Peacock-Farrell.
Blues did not take long to get themselves back into the game though, with Willum Willumsson pulling a goal back in the 24th minute when he was afforded too much space in the box and poked Emil Hansson’s simple cross beyond Jed Steer.
It was 2-2 four minutes into the second half when Jay Stansfield’s shot took a wicked deflection off of Oscar Wallin before creeping in at the far post.
Birmingham then went ahead for the first time in the 66th minute when Bielik beat Hector Kyprianou to head home from Tomoki Iwata’s cross, and that proved to be enough to secure the win.
