A late try from Tom Casson helped Harlequins claim a 31-28 victory over London Irish in an entertaining Aviva Premiership spectacle on Sunday.
Ian Humphreys and Ben Botica kicked three penalties each for Irish and Quins respectively to go alongside tries from Guy Armitage and Danny Care as the score was tied at 16-16 at the break.
Tom Williams touched down for the away side in the second period, but four penalties from the hosts' fly-half put them ahead before centre Casson's dramatic late and controversial score.
It was the visitors who set their intentions early when Botica kicked two penalties, but the New Zealander was at fault for the hosts' opening score when his kick was charged down and that allowed Armitage to pounce. Humphreys converted as Irish led 7-6 after 13 minutes.
Their advantage didn't last long as Anthony Watson's attempted offload fell into arms of Care and the scrum-half scampered over.
Successive penalties from the home side's stand-off levelled the scores before Botica kicked one of his own to regain Harlequins' lead.
But a further penalty from Humphreys meant the teams went into half-time level, although Quins were down to 14 men after Mike Brown's yellow card for a deliberate knock-on.
The respective fly-halves traded kicks from the tee early in the second period before a wonderful move from the visiting backline ended in Williams crossing in the corner.
The hosts' Irish fly-half cut that deficit with two more penalties before another seven minutes from time looked to have won the game. However, Casson latched on to Ugo Monye's offload to go over and send them top of the Aviva Premiership standings.
For London Irish:
Pen: Humphreys 7
Tries: Care, Williams, Casson
Con: Botica 2
Pen: Botica 4
London Irish: 15 Anthony Watson, 14 Topsy Ojo, 13 Jonathan Joseph, 12 Guy Armitage, 11 Sailosi Tagicakibau, 10 Ian Humphreys, 9 TomÃ¡s O'Leary, 8 Chris Hala'ufia 7 Jamie Gibson, 6 Declan Danaher (c), 5 Matt Garvey, 4 Bryn Evans, 3 Halani Aulika, 2 David Paice, 1 Max Lahiff.
Replacements: 16 Scott Lawson, 17 Cai Griffiths, 18 Leo Halavatau, 19 Kieran Low, 20 Ofisa Treviranus, 21 Alex Gray, 22 Steven Shingler, 23 Darren Allinson.
Harlequins: 15 Mike Brown, 14 Tom Williams, 13 Matt Hopper, 12 Tom Casson, 11 Ugo Monye, 10 Ben Botica, 9 Danny Care, 8 Nick Easter, 7 Chris Robshaw (capt), 6 Tom Guest, 5 George Robson, 4 Olly Kohn, 3 James Johnston, 2 Rob Buchanan, 1 Joe Marler.
Replacements: 16 Dave Ward, 17 Mark Lambert, 18 Will Collier, 19 Charlie Matthews, 20 Maurie Fa'asavalu, 21 Karl Dickson, 22 Rory Clegg, 23 Seb Stegmann.
Referee: Tim Wigglesworth
Assistant referees: Stuart Terheege, Roy Maybank
Television match official: Graham Hughes
Timekeeper: Roy Marfleet
Assessor: Ed Morrison