Gloucester reclaimed the summit of the Guinness Premiership with a brave 25-17 victory over London Wasps at Adams Park on Sunday, bringing the home side's eight-game winning run to an abrupt end.
The Cherry and Whites surged into an early 15-3 lead with tries from James Simpson-Daniel and Mike Tindall and, although Wasps threatened a comeback, Olly Morgan's second-half try was enough to secure the win.
Gloucester will be guaranteed a home semi-final if Wasps fail to pick up maximum points in midweek against Newcastle.
RaphaÃ«l IbaÃ±ez scored once in each half to set up a grandstand finish but Wasps eventually left Adams Park empty-handed as Ryan Lamb's injury-time penalty denied them a losing bonus point.
With Sale winning at Harlequins, Wasps dropped out of the top four but they do have a game in hand over play-off chasing rivals Harlequins and Leicester.
Gloucester were the last team to beat Wasps in the league, at Kingsholm on January 26, but they had not won away against their London rivals in 18 long years.
It took barely 10 minutes for the Cherry and Whites to threaten that record as they hit Wasps with an early assault and took a 12-0 lead.
Wasps full-back Josh Lewsey spilled a high ball under pressure from Iain Balshaw and Simpson-Daniel scooped up the loose ball to open the scoring inside three minutes.
Gloucester kept the tempo high with excellent off-loads from Italian lock Marco Bortolami and Fijian flank Akapusi Qera and continued to force Wasps backwards until Tindall cut a brilliant angle to beat Joe Worsley's attempted tackle and power over for the try.
Wasps found little change from Gloucester's powerful, aggressive defence led by another huge tackling performance from inside centre Anthony Allen.
Cipriani missed two penalty shots at goal as Wasps struggled to find a foothold in the game.
But Wasps have not rallied from the depths of the Premiership by panicking and they soon marched back into the contest.
Cipriani slotted his third shot at goal after Gloucester were forced into some scrambled defence when Ibanez threw a short line-out to Simon Shaw, the kind of quick-witted move which accounted for Leicester in last year's Heineken Cup final.
Although Lamb added three more points for Gloucester, Wasps had their tails up and Voyce sparked another telling attack by cutting inside off his wing.
Paul Sackey continued the move and Wasps earned another penalty as Carlos Nieto was penalised and sin-binned for killing the ball.
Lawrence Dallaglio opted for the line-out and Ibanez peeled off the back of a powerful Wasps driving maul to score.
Wasps piled forward and would have scored a second try just before the interval had it not been for some defiant goal-line defence, particularly from Scottish scrum-half Rory Lawson who halted Fraser Waters with a brilliant last-ditch tackle.
But Gloucester opened the second half as they did the first - with a try in the opening minutes.
Simpson-Daniel did well to claim a cross-kick from Lamb, beat Lewsey and then slipped a deft outside pass to Olly Morgan for the try.
Wasps were out of sorts and there was no clearer indication of that than the sight of Cipriani and scrum-half Eoin Reddan being replaced after just 57 minutes.
But they were not out of determination or good fortune.
Again Wasps kicked a penalty for touch and again they were rewarded. Gloucester stole the line-out but as the ball bounced loose Ibanez was alert and dived on it for his second try of the game.
The try set up a frantic finale as Wasps tried desperately to find an opening but Gloucester defended resolutely.
And Lamb then applied the metaphorical kick in the teeth with a late penalty to deny Wasps the losing bonus-point.
For London Wasps:
Tries: IbaÃ±ez 2
Cons: Cipriani, Staunton
Tries: Simpson-Daniel, Tindall, Morgan
Pens: Lamb 2
London Wasps: 15 Josh Lewsey, 14 Paul Sackey, 13 Fraser Waters, 12 Riki Flutey, 11 Tom Voyce, 10 Danny Cipriani, 9 Eoin Reddan, 8 Lawrence Dallaglio (c), 7 Tom Rees, 6 Joe Worsley, 5 Tom Palmer, 4 Simon Shaw, 3 Tim Payne, 2 RaphaÃ«l IbaÃ±ez, 1 Tom French.
Replacements: 16 Joe Ward, 17 Michael Holford, 18 George Skivington, 19 James Haskell, 20 Mark McMillan, 21 Dominic Waldouck, 22 Mark van Gisbergen.
Gloucester: 15 Olly Morgan, 14 James Simpson-Daniel, 13 Mike Tindall, 12 Anthony Allen, 11 Iain Balshaw, 10 Ryan Lamb, 9 Rory Lawson, 8 Luke Narraway, 7 Akapusi Qera, 6 Alasdair Strokosch, 5 Alex Brown, 4 Marco Bortolami (c), 3 Carlos Nieto, 2 Andy Titterrell, 1 Nick Wood.
Replacements: 16 Olivier Azam, 17 Alasdair Dickinson, 18 Will James, 19 Peter Buxton, 20 Gareth Delve, 21 Gareth Cooper, 22 Willie Walker.
Referee: Wayne Barnes
Touch judges: Stuart Terheege, Paul Emerson
Coach: Clive Leeke
Television match official: John Burtenshaw