Kenny Logan stroked his touch-line conversion between the posts and then thumped over a 50-metre penalty to propel his club-mates past the chequered flag.
The Exiles could not reproduce the high velocity wide game with which they have illuminated this season's Premiership. But while Dick Best, their coach, put forward the narrowness of the Loftus Road pitch as a mitigating factor, it was rather like blaming a major mechanical breakdown on a faulty door handle.
The Irish were taken to the cleaners up front, both at the line-out and by a Wasps front row that announced itself as the most accomplished and imaginative in the domestic game.
Will Green and Adam Black, the two props, were a constant pain in the Exiles' nether regions, running shrewd angles off their half-backs and loose forwards and turning their opponents with textbook wrap-up tackles.
And then there was Trevor Leota, that unique force of nature from Samoa. The potato-shaped hooker reduced the opposing pack to rubble with the sheer ferocity of his multi-faceted contribution and it is no exaggeration to suggest that he single-handedly gave a record 11,500 crowd a handsome return on their turnstile investments.
In fact, Leota went off the boil towards the end of a frantic encounter, largely because he damaged his left knee in the course of one of his countless furious rampages into the weakening underbelly of the Irish defence.
But he stayed on - wisely, the Wasps physios tend not to argue in such circumstances - and claimed the final word by burrowing into a driving maul to deliver a prime piece of possession from which Eben Rollitt cleverly conjured Dallaglio's decisive strike.
Two blanket defences ensured a 3-3 stalemate at the interval, but Wasps had edged the territorial contest in the first 40 and were in no mood to relinquish that advantage. They hit the ground running from the restart, nudged themselves ahead through a thoroughly remarkable 45-metre drop goal from Gareth Rees and then set up camp in and around the Irish 22.
Logan's second penalty, awarded against Neal Hatley for dropping a scrum near his own line, was a sure sign that dominance had been achieved and in the final quarter it was all Dallaglio and company.
"We keep on promising things and failing to deliver," said Dallaglio. "We won well at Saracens and then lost at West Hartlepool; we gave Bath a seeing-to and then went down at Bedford.
"It's about time we achieved some consistency and this should give us the platform to do it."
Very true, always assuming that his clubmates rediscover their breath in time for the next match.
Wasps: Try Dallaglio; Conversion Logan; Penalties Logan 3; Drop goal Rees. London Irish: Penalty Woods.
Wasps: J Lewsey (G Rees, 39); P Sampson, F Waters, R Henderson, K Logan; A King (M Denney, 74), M Wood; A Black, T Leota, W Green, M Weedon (capt), A Reed (S Shaw, 65), L Dallaglio, P Scrivener (E Rollitt, 70), J Worsley.
London Irish: C O'Shea (capt); J Bishop (J Cunningham, h-t), N Burrows, B Venter, N Woods; S Bachop, K Putt; N Hatley, R Kirke, R Hardwick (K Fullman, 70), N Harvey, R Strudwick, J Boer, I Fea'unati, R Gallacher.
Referee: C White (Twickenham).Reuse content