Birmingham have secured promotion straight back to the Championship after beating Peterborough 2-1 on Tuesday night.
First-half goals from Alfie May and Taylor Gardner-Hickman wrapped up the required three points for the visitors.
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The Blues are now 17 points clear of third-placed Wycombe, who have just five matches remaining.
Chris Davies has seen his team lose just three matches on their way to making an immediate return to the Championship.
It comes after their 13-year stay in the second tier was ended by relegation last term.
Birmingham had headed to the Weston Homes Stadium knowing a win or dropped points for Wycombe would clinch promotion.
Although the Chairboys were victorious away to Huddersfield, the Blues took matters into their own hands by winning on the road.
The travelling side got off to the perfect start as May opened the scoring with his 15th league goal of the campaign.
However, Posh equalised just three minutes later through Kwame Poku.
Gardner-Hickman restored Birmingham’s lead eight minutes before the interval, though, with what proved to be the winner.
His strike cued chaotic scenes in the away end which were replicated at the final whistle as their Championship return was sealed.
Following the match, Davies said: “A special night obviously it means the world to see the fans celebrate, it really is something special.
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“I have said previously how the club has suffered a lot, particularly in the last couple of years.
“It is about creating memories, bringing them some joy and making them proud of their club and I think that we have done that this season, so for me it means the world.”
Davies is in his first managerial post after being appointed at St. Andrew’s last summer.
His side are now the first Football League club to confirm their promotion this season with six still to play.
They also join relegated Southampton as the second team finalised in next term’s Championship line-up.
Meanwhile, Birmingham could be crowned champions on Saturday without even playing if Wrexham fail to beat Wigan away from home on the same day.
It would be the second time they have won the third tier title following their previous triumph in 1995.
Blues are also eyeing a League One record points tally, which was set back in 2014.
Wolves ended the 2013/14 campaign on 103 points after 46 matches.
Birmingham need just nine points to beat the record and could still end the season on as many as 113 points.
They could also lift another piece of silverware this weekend in the EFL Trophy.
The Blues face Peterborough once again on Sunday, this time at Wembley Stadium, looking to become three-time winners of the cup.