George Head's stoppage-time try secured Harlequins a 26-24 win over London Irish in a tense Premiership encounter.

Tommy Allan pulled a try back soon after the break as Irish had Donnell sent off before Ollie Hassell-Collins got a third for the Exiles.

But Alex Dombrandt and Allan levelled before Quins' Nick David got a red card as Paddy Jackson slotted a 70th-minute penalty before Head's try.

The score, in the fifth minute of stoppage time, was controversial after Irish felt Charlie Matthews tackled Benhard Janse van Rensburg while he was in the air just before.

The win sees Quins move up to third in the Premiership while Irish go up a place to 10th thanks to their losing bonus point.

Former Wasps winger Josh Bassett was just seven minutes into his Quins debut when he mishandled an attempt to intercept a pass and was sin-binned for a deliberate knock-on.

From the resulting penalty and close-range lineout, Fa'asa'o rumbled in with ease to put Irish ahead but the sides were levelled up soon after when Nick Simmons was yellow-carded for a high challenge on David.

But Donnell extended the lead three minutes later after Ben Loader superbly out-jumped David to gather Jackson's pinpoint high kick to allow the forward to go in.

Quins could have been level at the break, but a combination of good defending to stop a Wilco Louw break, and misfortune for Allan - whose long-range pass to George Hammond in the corner was forward - contributed to the hosts going into the break pointless.

Three minutes after the interval it seemed as though the game would turn as Allan ran in from close range, while replays showed that, in the build-up, Donnell went in with a shoulder on Joe Marler's head which saw the first-half try-scorer sent off.

But despite having 14 men it was Irish that got a third try as a lovely five-pass flowing move from halfway ended with Hassell-Collins going over in the left corner,

But close-range scores from Dombrandt and Allan in the space of 10 minutes saw the scores draw level and the hosts looked as though they would go on and win it.

But David's red card for a high hit on Luca Morisi tempered their ambitions and it seemed as though they would be on the end of as defeat when Jackson slotted a 70th-minute penalty.

But at the death - after Matthews's controversial incident - Quins won a penalty, kicked to the corner and from the resulting lineout worked a maul which saw Head bundled over for the winner in the 84th minute.

Harlequins head coach Tabai Matson:

"It's great to watch as a fan, but as a coach, jeepers, it's frustrating, especially the first half for us.

"But ultimately it's such a tight competition, this was never going to be an easy fixture and to scrape away with a win in the 84th or 85th minute is probably the most important thing.

"Disappointingly, their second-half try looked really soft for us and we just made a couple of really poor defensive glitches and they're sharp.

"One of the things I admire about them is that they're good in the wider channels, but we stayed in the fight and we talk about the composure at the end, when you're getting reds and yellows and people are playing in different positions.

"It's really tough so to be composed right at the end and get the win, there'll be a few pats on the back."

London Irish director of rugby Declan Kidney:

"When you lose in the last play of the game it is disappointing, but what you have to do as professionals is let the emotions settle and deal with it.

"We know there are lots of things we can do better, but you can't be that disappointed if you are that close.

"We were well out of the blocks but there are parts we can do better.

"It is very disappointing and there were lots of little bits in the last couple of minutes where the emotions were yo-yoing, so we have to take a look at what we can do better.

"When the emotion settles you come off and everyone is talking about the last couple of plays of the game, but what you have to do is look at the whole."

Harlequins: David; Marchant, Anyanwu, Esterhuizen, Bassett; Allan, Care; Marler, Musk, Louw, Hammond, Herbst, Kenningham, Evans, Dombrandt.

Replacements: Head, Baxter, Kerrod, Matthews, White, Gjaltema, Edwards, Beard.

London Irish: Parton; Loader, Morisi, Janse Van Rensburg, Hassell-Collins; Jackson, Englefield; Goodrick-Clarke, Willemse, Chawatama, Munga, Simmons, Basham, Donnell, Fa'aso'o.

Replacements: Creevy, Gigena, Hoskins, Ratuniyarawa, Gonzalez, Powell, Cinti Luna, Stokes.

Referee: Craig Maxwell-Keys