Ten-man MK Dons upset the odds to condemn League 1 leaders Brighton and Hove Albion to a 1-0 defeat at stadiummk thanks to Daniel Powell's seventh goal of the season.
A superb performance from every member of Karl Robinson's Dons team was richly rewarded with three points against a Brighton side who had only tasted defeat four times in this League campaign prior to the match.
The Dons took a first-half lead when Powell headed home at the far post after a flurry of shots failed to find their way through, but the home side were dealt a blow when Sean O'Hanlon was dismissed in the 67th minutes for his second caution.
Yet, even with 10 men the Dons were comfortable as the defence turned in a solid performance and David Martin pulled off some fine saves - including a superb double from Chris Wood - to ensure victory. The result keeps Robinson's Dons in the play-offs in sixth place.
Brighton's intent to attack was obvious from the first whistle as Gus Poyet's men set-up in a 4-3-3 formation and seized early control of the ball. However, the Dons' patient play allowed them to register two decent half-chances in the opening five minutes.
First Keanu Marsh-Brown, fresh from extending his loan from Fulham until the end of the season, broke free on the left flank and found a neat back heel to provide Peter Leven the opportunity to fizz a cross in for Daniel Powell, who had his shot well blocked by Adam El-Abd.
Moments later Powell was again in the thick of it as he tried to get on the end of Dean Lewington's cross, but both he and goalkeeper Casper Ankergren collided leaving the Brighton defence chance to clear the loose ball.
Aside from the opening five minutes, the Dons bossed proceedings and continued to look the more likely to net an opener as Marsh-Brown forced a brilliant tip over the bar by Casper Ankergren when Leven's long throw was cleared to him at the edge of the box. The first-time effort had a deceiving dip and the Brighton goalie did well to lift the shot over the bar.
Brighton spurned a glorious opportunity to break the deadlock when Elliott Bennett kept Inigo Calderon's deep cross in play at the by-line, only for Glenn Murray to fail in finding the touch to prod home the ball as it trickled along the goalmouth.
With 26 minutes on the clock Dons goalkeeper Martin was called to make his first real stop of the game, and it was the simplest of saves from the number one as Bennett's central free-kick from 35-yards was sent straight at him.
And, from the resulting free-kick Dons found a way through the Brighton defence to fire themselves in front. The Seagulls' defence was pulled apart with an array of shots fired into a crowed box, as Rowan Vine and Mathias Kouo-Doumbe both had low driven efforts well blocked before O'Hanlon's header hit the far upright.
At that point the Dons must have thought they had another frustrating afternoon in front of goal ahead of them, but Powell was on hand at the right of the box to nod the follow-up past Ankergren. A deserved lead for the Dons, and although Brighton began to feel their way back into the match the home side took the 1-0 advantage in at half-time.
Dons could have doubled their lead within a minute of the season-half when Rowan Vine's through ball found the lively Powell, however the wide man's low effort fell inches off-target.
An action-packed game lived up to its pre-match billing as both sides went all out in an end to end encounter. The home side felt they should have had the chance to extend their lead from the penalty spot when Vine was sent tumbling a yard inside the Seagulls box under the challenge of Marcos Painter, but their claims were waved away by referee Carl Boyeson.
At the other end, Dons had 'keeper Martin to thank for maintaining their advantage when he pulled off two magnificent point-blank saves from Wood - the first from Calderon's cross which he parried and the second came from the follow-up. Recognising the importance of the blocks the Cowshed sang Martin's name in praise.
Every Brighton attack was responded to with pressure from the Dons and Marsh-Brown continued to be pivotal to all their bright play. The 18-year-old danced clear of three Brighton defenders before picking out Stephen Gleeson who, after ghosting into the box, was denied by the fingertips of Ankergren.
But, the Dons' task of holding on, if not bettering their lead, then became more difficult in the 67th minute when O'Hanlon's sliding challenge on Murray earned him his second caution leaving Robinson's men to hold off Brighton for 24 minutes with ten men.
However, rather than shutting-up shop the Dons made positive substitutions - bringing on Jabo Ibehre, Sam Baldock and Stephen Hughes - to strengthen the threat up front.
Brighton failed to make use of their one man advantage with Francisco Sandaza, freed by a diagonal cross, skipping past Gleeson, who had moved to right-back, only to shoot wastefully wide.
Inevitably, the visitors enjoyed a greater share of the ball in the closing stages, and peppered the Dons box with crosses but Gary MacKenzie, superb at the back, was quick to clear every ball.
The sound of the final whistle produced a roar from stadiummk - with each supporter recognising a huge result for the Dons.
MK Dons (4-2-3-1): Martin; Kouo-Doumbe, O'Hanlon, MacKenzie, Lewington (c); Leven, Gleeson; Powell (Ibehre 74), Chadwick, Marsh-Brown (Hughes 78); Vine (Baldock 78).
Booked: O'Hanlon, Chadwick.
Sent-off: O'Hanlon 67
Subs not used: Searle, Chicksen, Stirling.
Brighton and Hove Albion (4-3-3) Ankergren; Calderon (Sparrow 76), Greer (c), El-Abd, Painter (Taricco 84); Bennett, Dicker, Bridcutt; Wood, Barnes (Sandaza 55), Murray.
Subs not used: Brezovan, Elphick, Baz, Holroyd.
Booked: Greer, El-Abd
Referee: Carl Boyeson (East Yorkshire)
Attendance: 9, 327 (2,086 away)