Wasps came from behind to prevent London Irish from reclaiming top spot with a 33-25 win in the Aviva Premiership on Sunday.
Fly-half Dave Walder kicked 18 points after Irish had battled to an 18-16 lead heading into the last quarter.
Irish kept fighting and scored a third try in the 78th minute through Paulica Ion to seemingly snatch a losing bonus point, only for Walder to deny them with a last-minute penalty.
Ryan Lamb hooked a third-minute penalty well wide for the visitors, but Walder was more accurate three minutes later to edge Wasps in front.
Wasps were having problems in the front row with New Zealand referee Bryce Lawrence having a quiet word with England loosehead prop Tim Payne after two scrums collapsed.
And Payne was at fault again two scrums later, this time in front of his posts, gifting Lamb the chance to kick an equalising penalty.
Walder and Lamb both missed further penalty attempts before the game's first try arrived on 21 minutes.
Walder sparked it with a tap and go, Tom Varndell made yards up the left before stepping inside and, five passes later,
Steve Kefu found Ben Jacobs with a snappy pass and the big centre smashed through four tackles to score.
Walder added the conversion but Irish were quickly back on the board. Number eight Chris Hala'ufia thundered up the left and smashed Richard Haughton out of his path before flipping the ball inside to Paul Hodgson to score.
Lamb failed to convert and Walder increased the home side's lead with another successful penalty, but the referee then warned Wasps captain Tom Rees about his team conceding penalties at the breakdown.
And a case in point came three minutes from half-time when Payne conceded a stupid penalty, going offside as Topsy Ojo tried to make ground. Lamb kicked the goal and Payne was shown a yellow card.
Seconds from the break,
Wasps brought on Shaun Ruwers for Payne in a scrum and he promptly conceded a penalty as the home side struggled to cope with Irish tighthead Faan Rautenbach.
Irish changed kicker to full-back Jamie Lennard
but he shanked his long-range attempt from the left wing.
Irish made a cracking start to the second half, although referee Lawrence missed a blatant knock-on by loosehead Clarke Dermody in the build-up.
Wasps were not sharp enough as Irish powered forward from the kick-off. Lamb chipped the ball over the defence, Broster and Steffon Armitage challenged for it, Dermody knocked on and Daniel Bowden scooped up the loose ball and scored between the posts, a score greeted by howls of crowd protest.
Walder chipped three points off the lead with a well-struck penalty and after Irish squandered two try-scoring opportunities on the Wasps line, they were made to pay on 65 minutes.
Wasps switched direction off a scrum, Jacobs made a searing break and passed to Walder, whose pass sent Joe
Worsley racing for the line.
It took three defenders to halt the England flanker, but Joe Simpson dug it out and armed Kefu to score from close range with Walder converting.
And the game was settled on 74 minutes when Worsley slammed into Hala'ufia, turned over the ball and when Jacobs broke clear of the cover he lobbed a precise pass out to Varndell to raced home unchallenged.
For London Wasps:
Tries: Jacobs, Kefu, Varndell
Cons: Walder 3
Pens: Walder 4
For London Irish:
Tries: Hodgson, Bowden, Ion
Cons: Lamb 2
Pens: Lamb 2
London Wasps: 15 Mark Van Gisbergen, 14 Richard Haughton, 13 Ben Jacobs, 12 Steve Kefu, 11 Tom Varndell, 10 Dave Walder, 9 Joe Simpson, 8 Dan Ward-Smith, 7 Tom Rees (captain), 6 Joe Worsley, 5 James Cannon, 4 Simon Shaw, 3 Ben Broster, 2 Joe Ward, 1 Tim Payne.
Replacements: 16 Tom Lindsay, 17 Shaun Ruwers, 18 Bob Baker, 19 Marty Veale, 20 Serge Betsen, 21 Nic Berry, 22 Seb Jewell, 23 Jack Wallace.
London Irish: 15 Jamie Lennard, 14 Topsy Ojo, 13 Elvis Seveali'i, 12 Daniel Bowden, 11 Jonathan Joseph, 10 Ryan Lamb, 9 Paul Hodgson, 8 Chris Hala'ufia, 7 Steffon Armitage, 6 Kieran Roche, 5 Bob Casey, 4 Nick Kennedy, 3 Faan Rautenbach, 2 David Paice, 1 Clarke Dermody (captain).
Replacements: 16 James Buckland, 17 Alex Corbisiero, 18 Paulica Ion, 19 Matt Garvey, 20 Richard Thorpe, 21 Marcus Watson, 22 Chris Malone, 23 Darren Allinson.
Referee: Bryce Lawrence (New Zealand)