Crawley boss Richie Barker hailed his side's shock 2-0 win at Peterborough as one of the best results of his time in charge of the club.
Town wrecked high-flying Posh's best start to a season for more than half-a-century with a 2-0 triumph at London Road where a brace from veteran striker Gary Alexander did the damage.
Alexander broke the deadlock with a terrific volley from a tight angle in the 22nd minute after being picked out by a Billy Clarke cross.
And the 34 year-old was on hand to double the advantage when punishing some pitiful defending in the 64th minute.
Posh posed little threat as their six-match winning streak came to an abrupt end.
Striker Britt Assombalonga saw two strong shouts for a penalty ignored by referee Darren Bond in the closing stages.
Bond did dismiss Crawley man Mike Jones late on for collecting a second caution, but that did not stop the visitors coming within a whisker of a third goal when substitute James Hurst rifled inches wide.
Boss Barker said: "My players were fantastic as they executed our game-plan to the letter.
"I can't speak highly enough of them after producing a performance like that.
"We don't have the players to contain opponents for 90 minutes and that's not my style either.
"We are an attacking team and want to create enjoyable games to watch - that's the only way we know.
"It is right up there with the best results I've had at Crawley because of how well Peterborough have started the season.
"They are probably the best team to have played at League One level in the last three years, so to beat them and keep a clean sheet is a great effort."
Posh boss Darren Ferguson was left dismayed by the standard of his team's defending as they tasted defeat for the first time this season, but he was also quick to praise the performance of conquerors Crawley.
Ferguson said: "We didn't play with anywhere near the energy or tempo that I expect.
"We huffed and puffed, but never looked like getting back into the game after going behind.
"It's been a really good start, but we still have to get better at getting something out of games when things aren't going our way.
"I need to see a reaction from the first minute of training on Monday morning.
"The good thing for me is I have a strong squad and plenty of players waiting in the wings for an opportunity.
"All credit to Crawley though as they are a good team and I think they will be up there this season."