Late Fleck strike sinks Cobblers as Wilder's return ends in Sheffield United promotion celebration
Sixfields once again set the scene for Chris Wilder's second promotion in two years but this time it came at Northampton's expense as Sheffield United finally secured their long-awaited return to the Championship with a dramatic 2-1 victory on a sun-kissed afternoon.
Needing three points to wrap up what's been known for weeks, Wilder's Blades showcased why they are the division's outstanding team with a dominant second-half display to come from a goal down and take victory.
Both goals and the full-time whistle were greeted by a pitch invasions from overjoyed United fans who finally saw their side end a five-year stay in England's third tier.
It comes almost exactly a year to the day since Wilder led the Cobblers to promotion with a 2-2 draw against Bristol Rovers at Sixfields, and few of the home fans on Saturday would begrudge him this achievement with his boyhood club, even if it did come to the detriment of their side.
The 49-year-old was afforded the expected warm welcome on his first visit back to Northampton but that's where the hospitality ended as the two sides engaged in an entertaining and evenly-matched affair.
Marc Richards' sensational strike on the cusp of half-time fired the Cobblers ahead but whilst that was by no means a flattering score at the break, it did prompt a response from United.
Leon Clarke brought the visitors level with a fine finish of his own on the hour-mark before United put the gloss on a perfect afternoon through John Fleck's 88th minute winner.
The scenes at full-time, with hundreds of United fans chanting 'one Chrissy Wilder', were reminiscent of those 12 months ago when Northampton celebrated their own promotion.
For the Cobblers, the manner of this defeat was tough to take and goes down as only their second in seven games, but it should not sound any alarm bells given the quality of the opposition, especially as they more than matched the champions-elect for long periods.
They remain 15th in Sky Bet League One, six points above the drop zone.
Brendan Moloney made his first Cobblers start since November and replaced Aaron Phillips at right-back, while Luke Williams returned from injury to form part of a four-man midfield that also included John-Joe O'Toole.
There was further good news on the bench as Alex Revell featured in a match day squad for the first time since January having finally recovered from a persistent calf problem.
In front of an electric atmosphere at Sixfields, mostly generated by the buoyant 1,456 travelling fans, United had the better of the opening exchanges and almost took the lead in spectacular fashion when, inside five minutes, Samir Curruthers' looping volley smacked against the crossbar.
Jay O'Shea curled wide and Blades skipper Paul Coutts hooked over as the visitors maintained their early supremacy, although Northampton then had their first sights of goal through Paul Anderson and Richards, who were both well off target.
The game settled down thereafter as both sides jostled for control, before Simon Moore became the first of either goalkeeper to be forced into action when saving well low down from Michael Smith who had been released by Richards.
Adam Smith also had to be on his guard to gather John Fleck's sneaky free-kick moments later but, after a bright start, goalmouth activity had become increasingly rare.
The contest seemed set to go into half-time goalless when one minute of added time was announced, but it turned out that would be just enough time for Richards to hammer Town ahead.
Anderson started the move, winning the ball back deep inside his own half and then finding Smith, who in turn released Richards and the Cobblers skipper, with the angle getting tighter by the second, unleashed a thunderbolt that flashed into the top corner via post and bar.
It was the perfect time to score and put Northampton into a half-time lead, but United, now with Billy Sharp on, made a flying start to the second-half and were almost level instantly when Smith saved from Jack O'Connell and then David Buchanan smuggled clear.
James Hanson was also thrown on by Wilder, although despite losing at Sixfields, his side were on the way up after news filtered through that Oldham had doubled their lead against third-placed Fleetwood Town.
And to make things even better for the boisterous away end, their side were back on level terms on the hour-mark.
It came out of the blue but the goal was clinically taken by Clarke who, having found himself through on goal, lifted into the roof of the net, sparking a mass pitch invasion from the Blades fans.
They could have turned the game around completely just seconds later but Chris Basham was thwarted at close-range by Smith before the Town goalkeeper also denied Sharp as United cranked up the pressure.
Revell and Shaun McWilliams were both brought on by Justin Edinburgh in an attempt to stem the tide but whilst those changes did help to some extent, Northampton were again indebted to Smith who blocked Fleck's low effort from a short corner.
United's pressure subsided after that intense spell, however, and given events elsewhere, it appeared they were content with the point as time ticked away without much incident.
But the Cobblers have specialised in late drama this season and there was to be another dose of it here, this time with less than three minutes left.
A hopeful ball over the Northampton defence found the hosts wanting and Sharp hooked in a cross to Fleck who got the better of two defenders and scrambled past Smith to win it and prompt another pitch invasion.
That was the goal that won both the game and promotion for United and after five rather incident-free minutes of added time, their return to the Championship was confirmed, much to the unbridled joy of fans and players.
Cobblers: Smith, Moloney, Diamond, Nyatanga, Buchanan, P Anderson (McWilliams 70), O'Toole, Taylor, Williams (McDonald 81), Smith (Revell 70), Richards (c)
Subs not used: Cornell, Phillips, McCourt, K Anderson
Blades: Moore, Basham, O'Connell, Wright, Freeman, Lafferty, Fleck, Coutts (c), O'Shea (Hanson 53), Carruthers (Sharp 45), Clarke (Ebanks-Landell 81)
Subs not used: Long, Done, Duffy, Chapman
Referee: Mark Heywood
United fans: 1,456