Wasps (3) 29
Tries: Voyce, Haskell 2, Hart
Cons: Cipriani 3
Pen: Cipriani
Gloucester (14) 26
Tries: Lawson, Azam, Morgan, Balshaw
Cons: Lamb 3
Wasps completed a stunning last-quarter fightback with a John Hart try four minutes from time to deny Gloucester victory in the EDF Energy Cup.
The visitors led 26-8 with 15 minutes left after Iain Balshaw scored their fourth try on the hour.
Rory Lawson, Olivier Azam and Olly Morgan had all touched down earlier.
But two tries in seven minutes from James Haskell brought Wasps to within four points before Hart plunged over 20 seconds from the end of normal time.
Danny Cipriani added his third conversion and Wasps held on in injury-time to complete a superb comeback win.
It was only their second victory in eight matches this season, with 10 players away on World Cup duty.
606: DEBATE
Haskell, controversially omitted from England's final World Cup squad, went over in the 66th and 73rd minutes, both tries converted by Cipriani, who had switched from full-back to fly-half.
Gloucester replacement Gareth Delve appeared to have denied Wasps victory with a desperate ankle-tap tackle on Sackey.
But the Wasps forwards drove over the Gloucester line again for the winning try, credited to replacement Hart, who had taken over from an ineffective Dallaglio.
Earlier, Gloucester took the lead when scrum-half Lawson wrong-footed the home defence with a delightful dummy before a spell of forward pressure saw Frenhc hooker Azam forced his way over.
Ryan Lamb converted both for a 14-0 lead, Wasps' only first-half reply a penalty from Cipriani as Wayne Barnes, returning to action after refereeing the controversial France-New Zealand World Cup quarter-final, made himself unpopular with the home fans by disallowing a 10th-minute Sackey score.
Lamb and James Simpson-Daniel combined to send full-back Morgan over in the right corner for a converted try before Tom Voyce breached Simpson-Daniel's tackle to score Wasps' opening try.
When Anthony Allen and Morgan set up Balshaw's try in the 61st minute, Wasps looked dead and buried.
But Gloucester captain Peter Buxton was sin-binned for the final 10 minutes and the hosts pressed home their advantage to complete a remarkable turnaround.
"I spent a lot of the week on the back foot and I spent a lot of the 60 minutes I was playing on the back foot but it's great.
"I can put all that other stuff to one side. Nobody has mentioned anything to me at the club this week about anything other than playing this weekend."
"We kept kicking the ball back to them and invited them in. I'm disappointed."
Wasps: Cipriani, Sackey, Waters, Hoadley, Voyce, Flutey, Reddan; Payne, Ward, Adams, Skivington, Birkett, Leo, Rees, Dallaglio.
Replacements: Ibanez, Holford, Hart, Haskell, Amor, Walder, Van Gisbergen.
Gloucester: Morgan, Balshaw, Simpson-Daniel, Allen, Foster, Lamb, Lawson; Wood, Azam, Nieto, Buxton (capt), Brown, Strokosch, Qera, Narraway.
Replacements: Titterrell, Collazo, James, Delve, Prendergast, Paterson, Vainikolo.
Referee: Wayne Barnes (England)
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