London Irish kept their slim top four hopes alive and dented Harlequins' play-off chances as a second-half Topsy Ojo try eventually broke down a resilient Quins defence.

The game started at a frenetic pace as both sides' young guns attempted to gain the early territory but it was Irish who gained the early initiative after a hospital pass from star Danny Care was knocked on by full-back Mike Brown and led to a prolonged period of home pressure.

But time and time again the Heineken Cup semi-finalists failed to turn possession into points with Ojo knocking on yards from the whitewash after a sublime pass from fly-half Shane Geraghty.

The hosts then wasted a golden opportunity to take the lead in the 15th minute as Peter Hewat struck the post with his penalty after Harlequins were penalised for putting their hand in the ruck.

The stalemate was eventually broken in the 35th minute as Bristol-bound Adrian Jarvis converted a penalty from 40 metres after the hosts had been penalised for collapsing the scrum.

It was more of the same after the break as the hosts pinned Harlequins in their own half but Hewat was again guilty of wasting their best point-scoring chance as he sent a 40-metre penalty sailing well wide in the 44th minute before being replaced by Eoghan Hickey two minutes later.

Irish than had a try disallowed in the 49th minute as some huge Quins defence from Ugo Monye forced Declan Danaher to knock the ball on over the line after fantastic hands from Seilala Mapusua and Richard Thorpe had freed the back rower.

But Irish continued to knock on the Quins door and in the 66th minute they finally broke through as Brown paid the price for his sides' repeated infringement and was sin binned for coming in at the side - with Hickey dispatching the resulting penalty.

And minutes later the hosts went in front as Hickey converted his second penalty of the match from in front of the posts after Mike Ross had been penalised for coming through the middle of the ruck.

Irish sealed the points in the 76th minute as Mapusua spilt Quins open and floated a long pass out to Ojo and the deadly winger beat the defence to the corner to touch down - with Hickey converting the tough conversion from the touchline.

Home captain Bob Casey was sinbinned from the resulting kick-off for deliberately obstructing the Quins attack and Jarvis kicked the consolation penalty for the visitors.