Connacht produced perhaps the greatest upset in the history of the European Cup in beating four-time champions Toulouse 16-14 on Sunday.
Connacht, who had lost 10 successive matches since recording their only win of the season over Italian side Zebre in the European Cup opening pool game, had former Scotland flyhalf Dan Parks to thank largely for their success as he scored 11 points.
Sterling defence also played a role after a try by their scrumhalf Kieran Marmion in the 47th minute, set up by a brilliant offload by Robbie Henshaw, restored the lead they had held for most of the first-half.
Henshaw himself was unfortunate to have a second try ruled out after a review by the video referee later in the second-half. Toulouse, who got back into the game with a try by France captain Thierry Dusautoir 15 minutes from time, did manage to come away with a bonus point to put them level on points with table-topping Saracens.
Connacht are third just a point behind them and will be looking to complete a famous double next weekend over the French giants.
Earlier on Sunday Connacht's more lauded compatriots, two-time European champions Munster, went top of Pool Six after an impressive 36-8 demolition of previous tabletoppers Perpignan in Limerick.
Munster have a two-point lead over English outfit Gloucester, who beat Edinburgh 23-12 in Scotland. Perpignan are third on six and Edinburgh on four with three games remaining.
Munster took the game by the scruff of the neck from the start and by the 35th minute were 22-0 up having scored three tries, the last one a scintillating 45-metre solo effort by Irish international Keith Earls down the right wing.
Flank Sean Dougall had scored the opener which had stemmed from a poor clearance kick by James Hook, Irish scrum-half Conor Murray producing a lovely offload in the move that led to Dougall touching down.
Prop Dave Kilcoyne added the second barrelling over from a short distance out. Hook landed a penalty early in the second-half as Perpignan tried to get back into the match and become the first French side to win at Thomond Park in the tournament's history.
Not such good news for the Irish side was that neither of their halfbacks lasted long in the second-half, Murray going off and having his right knee placed in a knee brace while flyhalf Ian Keatley also trooped off rather gingerly.
The hosts got what could prove to be a crucial bonus point in the 65th minute when the referee awarded them a penalty try when Kisi Pulu committed a professional foul in trying to stop them going over.
He was sin-binned for his actions and replacement flyhalf JJ Hanrahan converted for 29-3.
Munster No.8 James Coughlan added a fifth try three minutes from time which Hanrahan also converted and although Joffrey Michel scored a consolation try for Perpignan the French side will need to raise their game considerably for next weekend's rematch.
However, man-of-the-match Earls admitted that his side too needed to improve in certain areas, which fortunately for them they had not been punished by a lacklustre Perpignan side.
"I think we need to improve another 30 percent," said the 26-year-old. "Defensively we were caught out, myself on two occasions, so we have some work to do.
"It will be a tough task in France but we got a good result there two years ago."
Also on Sunday another two-time winners Leicester beat Montpellier 41-32 in a humdinger of a game which included two tries for Tigers wing Miles Benjamin. With their attacking bonus point they are within two points of leaders Ulster.
All of Sunday's results and scorers:
Connacht 16-14 Toulouse
Tries: Barraque, Dusautoir
Cons: Barraque 2
Pens: Parks 2
Toulouse: 15 Clement Poitrenaud, 14 Yoann Huget, 13 Florian Fritz, 12 Yann David, 11 Hosea Gear, 10 Jean Pascal Barraque, 9 Jano Vermaak, 8 Louis Picamoles, 7 Thierry Dusautoir, 6 Yacouba Camara, 5 Yoann Maestri, 4 Edwin Maka, 3 Census Johnston, 2 Chiliboy Ralepelle, 1 Gurthro Steenkamp.
Replacements: 16 Jaba Bregvadze, 17 Schalk Ferreira, 18 Yohan Montes, 19 Romain Millo-Chluski, 20 Christopher Tolofua, 21 Jean-Marc Doussain, 22 Lionel Beauxis, 23 Timoci Matanavou.
Connacht: 15 Robbie Henshaw, 14 Fionn Carr, 13 Eoin Griffin, 12 Dave McSharry, 11 Matt Healy, 10 Dan Parks, 9 Kieran Marmion, 8 George Naoupu, 7 Jake Heenan, 6 John Muldoon, 5 Craig Clarke (captain), 4 Mick Kearney, 3 Nathan White, 2 Sean Henry, 1 Brett Wilkinson.
Replacements: 16 Jason Harris Wright, 17 Denis Buckley, 18 Rodney Ah You, 19 Michael Swift, 20 Eoin McKeon, 21 Frank Murphy, 22 Craig Ronaldson, 23 Gavin Duffy.
Referee: Marius Mitrea (Italy)
Assistant referees: Stefano Penne, Elia Rizzo (Italy)
TMO: Alan Falzone (Italy)
Leicester Tigers 41-32 Montpellier
Tries: Goneva, Benjamin 2, Gibson
Cons: Flood 3
Pens: Flood 4
Tries: Gorgodze, Nagusa, Berard 2
Cons: Pélissié 2, Trinh-Duc
Pens: Pélissié 2
Leicester: 15 Scott Hamilton, 14 Adam Thompstone, 13 Vereniki Goneva, 12 Dan Bowden, 11 Miles Benjamin, 10 Toby Flood (captain), 9 Ben Youngs, 8 Jordan Crane, 7 Julian Salvi, 6 Jamie Gibson, 5 Graham Kitchener, 4 Louis Deacon, 3 Dan Cole, 2 Tom Youngs, 1 Marcos Ayerza.
Replacements: 16 Neil Briggs, 17 Boris Stankovich, 18 Fraser Balmain, 19 Ed Slater, 20 Thomas Waldrom, 21 David Mélé 22 Blaine Scully, 23 Ryan Lamb.
Montpellier: 15 Anthony Floch, 14 Timoci Nagusa, 13 Rene Ranger, 12 Thomas Combezou , 11 Yoan Audrin, 10 Francois Trinh Duc (captain), 9 Jonathan Pélissié, 8 John Beattie, 7 Mamuka Gorgodze, 6 Kelian Galletier, 5 Mickael De Marco, 4 Jim Hamilton, 3 Maximiliano Bustos, 2 Charles Geli, 1 Naama Leleimalefaga.
Replacements: 16 Thomas Bianchin, 17 Mikheil Nariashvili, 18 Paea Fa'anunu, 19 Thibaut Privat, 20 Tulou, 21 Benoit Paillaugue, 22 Wynand Olivier, 23 Pierre Berard.
Referee: John Lacey (Ireland)
Assistant referees: Mark Patton, John Carvill (both Ireland)
TMO: Marshall Kilgore
Gloucester 23-12 Edinburgh
Tries: Tonks, Denton
Tries: Cook, Thomas 2
Pens: Burns 2
Edinburgh: 15 Greig Tonks, 14 Dougie Fife, 13 Nick De Luca, 12 Ben Atiga, 11 Jack Cuthbert, 10 Harry Leonard, 9 Greig Laidlaw (captain), 8 Dave Denton, 7 Ross Rennie, 6 Cornell du Preez, 5 Izak van der Westhuizen, 4 Grant Gilchrist, 3 WP Nel, 2 Ross Ford, 1 Al Dickinson.
Replacements: 16 Aleki Lutui, 17 Wicus Blaauw, 18 Geoff Cross, 19 Ollie Atkins, 20 Roddy Grant, 21 Grayson Hart, 22 Joaquin Dominguez, 23 Tom Brown.
Gloucester: 15 Rob Cook, 14 Martyn Thomas, 13 Henry Trinder, 12 Billy Twelvetrees (captain), 11 Jonny May, 10 Freddie Burns, 9 Jimmy Cowan, 8 Ben Morgan, 7 Matt Kvesic, 6 Sione Kalamafoni, 5 James Hudson, 4 Elliot Stooke, 3 Shaun Knight, 2 Darren Dawidiuk, 1 Yann Thomas.
Replacements: 16 Huia Edmonds, 17 Dan Murphy, 18 Rupert Harden, 19 Tom Hicks, 20 Matt Cox, 21 Dan Robson, 22 Mike Tindall, 23 Steph Reynolds.
Referee: Jerome Garces (France)
Munster 36-8 Perpignan
Tries: Dougall, Kilcoyne, Earls, Penalty, Coughlan
Cons: Keatley 2, Hanrahan 2
Munster: 15 Felix Jones, 14 Keith Earls, 13 Casey Laulala, 12 James Downey, 11 Johne Murphy, 10 Ian Keatley, 9 Conor Murray, 8 James Coughlan, 7 Sean Dougall, 6 Peter O'Mahony (captain), 5 Paul O'Connell, 4 Donncha O'Callaghan, 3 Stephen Archer, 2 Damien Varley, 1 Dave Kilcoyne.
Replacements: 16 Duncan Casey, 17 James Cronin, 18 BJ Botha, 19 Billy Holland, 20 CJ Stander, 21 Cathal Sheridan, 22 JJ Hanrahan, 23 Denis Hurley.
Perpignan: 15 James Hook (captain), 14 Joffrey Michel, 13 Tommaso Benvenuti, 12 Watisoni Votu, 11 Sofiane Guitoune, 10 Camille Lopez, 9 Tom Ecochard, 8 Justin Purll, 7 Al Strokosch, 6 Jean-Pierre Perez, 5 Guillaume Vilaceca, 4 Luke Charteris, 3 Paulica Ion, 2 Romain Terrain, 1 Sébastien Taofifenua.
Replacements: 16 Maxime Delonca, 17 Kisi Pulu, 18 Jean Baptiste Custoja, 19 Sébastien Vahaamahina, 20 Dewaldt Duvenage, 21 Tommy Allan, 22 Richard Haughton, 23 Dan Leo.
Referee: Greg Garner (England)