Michael Dykes scored a hat-trick on his Premiership debut as London Irish beat 14-man Harlequins in a high-scoring derby to boost their top-four hopes.

Quins, meanwhile, had captain Stephan Lewies sent off in between a penalty try and Tommaso Allan's effort.

Dykes got his third before Josh Bassett and Dino Lamb gave the visitors hope, but Tom Pearson settled it for Irish.

A fourth win in five Premiership outings sees London Irish move up to seventh in the table, one point behind Harlequins and two adrift of fourth-placed Northampton.

Dykes was handed his chance after Ollie Hassell-Collins was named in England's squad for the Six Nations, having scored eight tries in 12 Premiership outings this season, and the 21-year-old proved to be the perfect replacement.

Irish made a fast start at the Gtech Community Stadium as number eight Cunningham-Smith rounded off a rolling maul from a line-out in the fourth minute, and soon after Dykes finished a backs move from close range.

Dykes was then sent to the sin-bin for a deliberate knock-on to stop Nick David from crossing, which saw Quins awarded a penalty try, but Irish quickly restored their 14-point lead when Stokes picked up the loose ball following Danny Care's high kick and the full-back scampered in from outside the 22.

The task facing the visitors was made all the harder when flanker Lewies was shown red on 21 minutes for a dangerous clear-out on Cunningham-Smith at the breakdown, although Allan went over to make it 21-12 after a good break by David.

The Italy fly-half could not add the extras and the Exiles had their fourth when Stokes fed Dykes for his second in the corner on the stroke of half-time.

The winger's hat-trick was completed following the restart after Ben White capitalised on a gap in the defence, but a break from Andre Esterhuizen helped set up Leicester-bound Bassett to pull one back.

Lamb then stretched over and Allan converted to drag Quins to within 11 points with just over 15 minutes left.

However, a yellow card for prop Joe Marler halted their momentum and Pearson squeezed through a gap to extinguish any chance of a comeback, with Paddy Jackson adding his sixth conversion for a flawless afternoon off the kicking tee.

Quins picked up a bonus point to move level on points with Gloucester and remain just ahead of Irish, but Tabai Matson's side have now lost their past four Premiership fixtures.

London Irish head coach Les Kiss:

"We had to get our five points to make sure we stayed in the area [in the table] that we can put the other teams under pressure.

"With Ben Loader not being able to play and Ollie Hassell-Collins getting his opportunity with England, it is nice to know that you have got these young kids coming through who have got confidence.

"Dykesy backs himself and I think we saw that in his game. He is getting the reward for sticking at it for two years. He is a good lad and he makes selection harder and harder now.

"He has been playing well in the Premiership Cup and I am really happy for him."

Harlequins head coach Tabai Matson:

"You have got to tip your hat as they were really efficient and we couldn't slow their breakdown.

"Forty-two points is pretty tough to take. When you remove the circumstances, we are gutted.

"The reality is we are a mid-table team. Nice fightback, but too little too late.

"The good thing is we get time to recalibrate and move on. Clearly there is work to do for us."

London Irish: Stokes; Cinti, Van Rensburg, Jennings, Dykes; Jackson, White; Goodrick-Clarke, Creevy, Hoskins, Simmons, Coleman, Rogerson (capt), Pearson, Cunningham-South.

Replacements: Willemse, Fischetti, Parker, Ratuniyarawa, Gonzalez, Powell, Morisi, Arundell.

Sin-bin: Dykes (19).

Harlequins: Edwards; David, Beard, Esterhuizen, Bassett; Allan, Care; Marler, Head, Louw, Lamb, Herbst, Lewies (capt), Evans, Lawday.

Replacements: Musk, Baxter, Kerrod, Chisholm, Wallace, Steele, Anyanwu, Hyde.

Sin-bin: Marler (69).

Sent off: Lewies (21).

Referee: Matthew Carley.