Birmingham gave Sheffield Wednesday a lesson in finishing as they maintained their three-point lead at the top of the Championship at Hillsborough.
Stephen Clemence's angled drive fired Birmingham ahead on the stroke of half time, against the run of play.
Birmingham were again on the back foot when Gary McSheffrey doubled their lead with another clinical finish.
Cameron Jerome notched Birmingham's third in injury time, to give a the Blues a flattering margin of victory.
Sheffield Wednesday manager Brian Laws:
"It's the biggest travesty I've ever seen in my life.
"We were the better side and lost. We really took the game to them and I thought we were excellent. I can't understand how we haven't scored. But there are a lot of positives to come out of the game and I'll pick the players up."
"Mark Crossley went off because he felt his hamstring but it's not as serious as we first thought and I'll be very surprised if he's not ready for next week."
Birmingham manager Steve Bruce:
"We got away with it, it's as simple as that. That was as tough a game as we've had. Wednesday were excellent and the crowd was right behind them.
"But they couldn't do the vital thing, sticking the ball in the net.
"With Gary McSheffrey, Cameron Jerome and Nicklas Bendtner up front, we're always a threat. I wouldn't swap any of them for anybody."
Sheff Wed: Crossley, Bullen, Simek, Bougherra, Spurr, Lunt, Brunt, Andrews (MacLean 45), Folly (O'Brien 77), Tudgay, Burton (Talbot 76).
Subs Not Used: Adamson, Coughlan.
Birmingham: Maik Taylor, Kelly, Sadler, Upson, Jaidi, Clemence, Larsson (Danns 86), Nafti, McSheffrey (Kilkenny 85), Jerome, Bendtner (Campbell 90).
Subs Not Used: Doyle, Martin Taylor.
Booked: McSheffrey, Bendtner, Larsson, Upson.
Goals: Clemence 42, McSheffrey 65, Jerome 90.
Att: 26,083
Referee: G Laws (Tyne & Wear).