London Irish (13) 26
Tries: Hala'Ufia, Thorpe Cons: Hewat 2 Pens: Hewat 4
Wasps (0) 14
Tries: Rees, Reddan Cons: Van Gisbergen, Staunton
Champions Wasps started the defence of their Premiership crown with an error-strewn display at a wet Twickenham.
London Irish took an early lead through new signing Chris Hala'Ufia.
Peter Hewat converted and added two penalties to give Irish a 13-0 half-time lead and they went further ahead when Richard Thorpe crossed.
Wasps got on the board with a converted Tom Rees try, but Hewat added two more penalties and Eoin Reddan's converted try could not save the visitors.
Ian McGeechan's Wasps side are traditionally slow starters to the season and London Irish were far the more threatening side on Saturday.
The Experimental Law Variations have been the main talking point in the build-up to the season and one of the new rules was in evidence as Wasps paid the price for dropping numbers at an early line-out.
606: DEBATEThey used two fewer players than the Exiles in the sixth minute and looked on in horror as Richard Birkett's attempted catch deflected into the hands of Hala'Ufia, who burrowed over from close range.
The Tongan number eight was quickly transformed from hero to villain when he tripped Reddan at a free-kick and was dispatched to the sin-bin.
With a downpour making the ball very slippery handling was proving very difficult but the Irish dealt with the conditions better and two Hewat penalties gave them a healthy 13-0 half-time lead.
The champions' problems at the line-out proved costly once again in the 54th minute when Thorpe came up with the ball before swatting aside a poor tackle from Tom Voyce to cross.
Rees finally got Wasps off the mark as the match entered the final quarter, showing initiative to scamper through a static defence.
But two rapid penalties from Hewat put the result beyond doubt, despite a late Reddan try, which saw the Ireland scrum-half capitalise on a slip by Catt.
London Irish boss Toby Booth:
"Wasps came back at us and you expect that from them so to show the mentality to shut them out was fantastic.
"That was as encouraging a display as we could have asked for at this stage of the season.
"Sometimes denying the opposition a bonus point is as important as securing yours, so we're very pleased."
Wasps director of rugby Ian McGeechan:
"It was a sub-standard performance and we're all very disappointed. We conceded a couple of easy scores.
"We came back well, scoring two good tries, and if we had got one there we would have had the bonus point.
"Irish were hanging on at the end but when you have built up that sort of lead it doesn't really matter - a bonus point would have been fair reward for our endeavour in the second half."
London Irish: Hewat; Ojo, D Armitage, Mapusua, Tagicakibau; Catt, Hodgson; Corbisiero, Coetzee, Rautembach, Johnson, Kennedy, Thorpe, S Armitage, Hala'ufia.
Replacements: Hickey for Catt (65), Richards for Hodgson (72), D Murphy for Corbisiero (48), Buckland for Coetzee (60), Paice for Rautembach (60), Fisher for Hala'ufia (78).
Not Used: Thompstone.
Sin Bin: Hala'Ufia (16)
Wasps: Van Gisbergen; Sackey, D Waldouck, Lewsey, Voyce; Flutey, Reddan; Payne, Ibanez, Barnard, Shaw, Birkett, Worsley, Rees, Haskell.
Replacements: Mitchell for Van Gisbergen (68), Staunton for Lewsey (41), Webber for Ibanez (68), Vickery for Barnard (51), Palmer for Birkett (51), Hart for Haskell (68).
Not Used: Simpson.
Att: 52,087
Ref: Andrew Small (RFU).
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