Birmingham went top of the Coca-Cola Championship after a 1-0 victory at home to QPR in the lunchtime kick-off.
Kevin Phillips' solitary strike on the stroke of half-time was enough to lift Blues above previous leaders Wolves, who subsequently slipped to a surprise 3-1 defeat at Swansea.
The writing was on the wall in the first minute for Mick McCarthy's side when Jordi Gomez fired the Welsh club ahead. Andy Keogh equalised in the 16th minute only for Jason Scotland (41, 57) to score either side of half-time to complete victory.
Third-placed Reading closed the gap to two points with a 3-1 win at home to Burnley.
Noel Hunt scored in the fourth minute before brother Stephen made it two (52), and when Shane Long (64) added a third it made Chris McCann's 89th-minute reply no more than a consolation.
Sheffield United moved up to fourth, overtaking city rivals Wednesday, with a 3-0 success over Bristol City thanks to two goals from James Beattie either side of Liam Fontaine's own goal.
The Owls, by contrast, were hammered 4-0 at Plymouth, who were set on their way by Mark Beevers' 15th-minute own goal before Paul Gallagher (25), Jamie Mackie (30) and Marcel Seip (90) all got on the scoresheet to lift their side to fifth.
Cardiff moved up a place to sixth despite being held to a 1-1 draw at Blackpool after Alan Gow's 90th-minute equaliser cancelled out Paul Parry's goal for the Bluebirds seven minutes earlier.
Watford recovered from Preston defender Sean St Ledger's fifth-minute effort to win 2-1 with goals from Jon Harley (12) and Tommy Smith (21).
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