It was to get worse for Town, as Lee McCulloch put Wigan ahead on 18 minutes, with Jason Roberts putting the home side 2-0 ahead just three minutes later.
The two goals seemed to have an effect on Town, with the Suffolk side appearing to go through the motions in the second half, and clearly seeming to believe they were destined for the play-off's.
With five minutes to go Wigan put their promotion, beyond any possible doubt when Nathan Ellington netted their third, before Sidwell got a late consolation goal for Reading.
Although Town only managed a draw at Brighton, in the end it did not matter as Wigan won, which was always going to be enough to send them up automatically no matter what happened at Brighton.
However, the result between Town and Brighton did however matter for the home side, as the point was enough to keep them in the Championship for at least another season, with Gillingham facing the drop to League One after drawing 2-2 with Nottingham Forest.
Crewe meanwhile beat Coventry by two goals to one. In the end, Stan Ternant's Gillingham side were relegated by having a worse goal difference than Crewe by one goal, a testament to how tight it has been in this seasons relegation dogfight.
So to the teams battling for the Play-Off's. West Ham secured a tight 1-0 win over Watford to claim sixth place in the league and face Town in a repeat of last seasons play-off semi final. This time however, Town have the advantage of playing at home second.
In the battle for fourth place which took place between Derby and Preston this afternoon, it was George Burley's side that took the points at Pride Park, beating Preston by three goals to one giving Derby the advantage of playing at home second in their play-off semi final.
Click here for the Championship Ups and Downs for 2004/5