Tries from dazzling youngsters Jonathan Joseph and Tom Homer failed to save London Irish from defeat at the Aviva Premiership leaders.

Full-back Homer gave Exiles the perfect start when he crowned a superb period of possession by going over in the second minute.

He scored all his side’s points as they forged a 13-10 interval.

But all of that was overshadowed by the outstanding individual try scored by Joseph, which Homer converted to pull Exiles level at 20-20.

Coach Toby Booth said: “There is no limit to how good Jonathan Joseph can be. In the 10 years I have been at Irish he is one of the most talented people I have ever worked with.

“He is very mature for his age. I think it is a matter of when not if (he is selected for England).”

Quins, though, sealed victory when Ross Chisholm added to earlier tries by Tom Casson and Tom Williams.

Fly-half Nick Evans kicked 12 points, while scrum-half Danny Care added an unorthodox drop goal.

Irish grabbed a losing bonus point thanks to a late penalty by replacement fly-half Adrian Jarvis.

But Booth could not hide his frustration with the way his side handed two tries to their arch rivals.

Scrum-half Darren Allinson’s clearance kick was charged down by George Robson for Williams to score and then Dan Bowden’s chip-kick bounced kindly for Williams, who counter-attacked quickly up the right before providing a grubber-kick for Chisholm to gather and hold off Homer before going over.

Booth said: “I am bitterly disappointed because I thought we were very good for the effort.

“But a couple of key moments cost us dear. They got 14 points from a kick chargedown and a counter-attack from a chip-through near to their posts.

“Those two tries came from kick-chases and we contributed to them. The best defences in the world can’t defend them.

“We will have to look at the decisions we made. Did we make the right ones? Certainly for Dan Bowden’s little chip that they went 70 metres for. That was absolutely the right decision. There was nobody there. It bounces left we score, it bounces right, they score.

“We won’t stop playing that’s for sure. That is not what we are about.

“Everyone is a little bit flat in the changing-room because the endeavour was good.

“They had two chances and they took them. That is credit to Harlequins but that is how cruel a master professional sport can be.”

Booth continued: “As a fixture you had to love it. There was a lot of quick ball and a lot of positive intent from two sides who went for it.

“If we can produce fixtures in the Premiership like that then rugby is in a good place.”

“I don’t think anybody can argue with the quality of our back line. It had a nice balance and was very threatening with evasiveness and pace.

“As well as youngsters like JJ, Marland (Yarde) and Tommy Homer, you have the experience of Topsy Ojo and Sailosi Tagicakibau and Delon Armitage.

“It is our challenge to keep them in the game as much as possible. But it bodes well for the future.”

Irish, who lost Shontayne Hape at half-time following a bang on the head that gave him double vision, have not given up hope clinching a top-four play-off spot.

Booth said: “We are going to make a contest of it.

“If we can get a bit more strength in depth – in the back row in particular – that will be great for us. Today we started with four second rows (Nick Kennedy, Bryn Evans, Matt Garvey and Kieran Roche).”

To see how the game unfolded click below.

The Exiles made five changes from the side that beat Gloucester in the LV= Cup last Saturday.

Ojo and Joseph replaced Adam Thompstone and Jonathan Spratt, while Roche, David Paice and Faan Rautenbach came into the pack with Brian Blaney and Paulica Ion dropping to the bench.

Quins made wholesale changes for the big London derby as they sought to end a run of three successive defeats.

Just four players from their starting line-up for last weekend's 45-40 defeat at Cardiff Blues retained their places - Chisholm, Casson, Sam Smith and Tom Guest.

Harlequins: 15 Ross Chisholm, 14 Tom Williams, 13 Matt Hopper, 12 Tom Casson, 11 Sam Smith, 10 Nick Evans, 9 Danny Care, 8 Nick Easter, 7 Luke Wallace, 6 Tom Guest, 5 George Robson (c), 4 Olly Kohn, 3 James Johnston, 2 Joe Gray, 1 Mark Lambert

Replacements: 16 Chris Brooker, 17 Aston Croall, 18 Tim Fairbrother, 19 Tomas Vallejos, 20 Will Skinner, 21 Karl Dickson, 22 Rory Clegg, 23 George Lowe.

London Irish: 15 Tom Homer, 14 Topsy Ojo, 13 Jonathan Joseph, 12 Shontayne Hape, 11 Sailosi Tagicakibau, 10 Dan Bowden, 9 Darren Allinson, 8 Richard Thorpe, 7 Kieran Roche, 6 Matt Garvey, 5 Bryn Evans, 4 Nick Kennedy, 3 Faan Rautenbach, 2 David Paice, 1 Clarke Dermody (c).

Replacements: 16 Brian Blaney, 17 Max Lahiff, 18 Paulica Ion, 19 Ed Siggery, 20 Marland Yarde, 21 Delon Armitage, 22 Adrian Jarvis, 23 Ross Samson.