|London Irish (10) 24|
|Tries: Hassell-Collins 4 Cons: Myler 2|
|Gloucester (3) 20|
|Tries: Chapman, Thorley, Rees-Zammit Con: Twelvetrees Pen: Twelvetrees|
Ollie Hassell-Collins scored four tries as London Irish leapfrogged Gloucester to move into the Premiership top five.
The England Under-20s winger scored a quick-fire double in the first half to help the Exiles into a 10-3 lead.
The 21-year-old then intercepted and raced 60m for his hat-trick score before Gloucester hit back with tries from Charlie Chapman and Ollie Thorley.
Hassell-Collins' fourth made it 24-15 but a late try for Louis Rees-Zammit gave Gloucester a losing bonus point.
It was a third league defeat in a row though for the visitors, who drop to seventh, while the Exiles surged to a third straight win.
The Exiles dominated the early exchanges but Billy Twelvetrees opened the scoring with a penalty on Gloucester's first foray into the hosts' territory after Thorley's counter-attack.
But Irish responded swiftly, a flicked pass from Nick Phipps to Stephen Myler after a five-metre scrum seeing the fly-half put Hassell-Collins over in the left corner.
It was far too easy from a Gloucester perspective, with their blind-side defence exposed, and the Exiles punished further lapses with their second try five minutes later.
Hassell-Collins brushed off a weak tackle from scrum-half Charlie Chapman, making his first Premiership start for Gloucester, and stretched over for his second score.
Twelvetrees missed a further penalty attempt before the interval as the visitors came back into it and they started the second period on the attack.
But Hassell-Collins picked off a pass on his own 22 to race away for his hat-trick try, Myler - who had missed his first two conversion attempts - this time adding the extras for a 17-3 lead.
Gloucester, to their credit, responded well and scrum-half Chapman danced his way over from a five-metre scrum, Twelvetrees landing the conversion to bring the visitors within range.
Thorley's superb finish in the corner made it a two-point game, with Twelvetrees unable to convert.
But a clever offload from Motu Matu'u - who started at hooker after the late withdrawal of Dave Porecki - saw Terrence Hepetema put Hassell-Collins over for his fourth try, and his seventh in the league this season, earning the Exiles a bonus point.
Gloucester replaced fly-half Danny Cipriani, playing the day after releasing an emotional video tribute to former girlfriend Caroline Flack, who took her own life last week, with youngster Lloyd Evans.
Matt Rogerson had a further try for the hosts disallowed by the TMO, and a smart finish from Rees-Zammit with eight minutes left - the teenager scoring his seventh league try of the campaign - ensured a tense finish.
London Irish winger Ollie Hassell-Collins:
"I'm over the moon as it's the first time I've scored four as in my early years I played mostly at centre for the Newbury club.
"My job is to finish and I'm grateful to the boys inside me for giving me the chances. The second one probably gave me the greatest pleasure as it was the most difficult to score."
Assistant coach Declan Danaher:
"We won on the back of Ollie's four tries but our early defensive effort in repelling them set our standard for the game.
"We could have kicked a couple of penalties but we back our players, who are making the on-field calls. We just have to keep improving and the boys are being constantly challenged to increase their efforts."
Gloucester head coach Johan Ackermann told BBC Radio Gloucestershire:
"We are not playing well at the moment if you look at the errors, but credit to the players, we were only one score away from winning it and that is the frustrating part.
"When we put our minds to it, we play well in stages but a lot of things didn't go our way. It started with the line-outs and then it filters through to not looking after the ball and today we had a few defensive errors as well.
"We are compounding error on error and then we are chasing the game. It isn't good enough, we are the first to acknowledge that, but it is not a lack of trying.
"The players really put themselves out there but the character of the team is going to be tested now. As a management and players, we must fix what has gone wrong, but it's not going to be easy."
London Irish: Loader; Williams, Rona, Hepetema, Hassell-Collins; Myler, Phipps; Hobbs-Awoyemi, Matu'u, Hoskins, Coleman, Van der Merwe (capt), Rogerson, Cowan, Tuisue.
Replacements: Fainga'a, Elrington, Kepu, Mafi, Donnell, Meehan, Campbell, Stokes.
Gloucester: Banahan; Rees-Zammit, Twelvetrees, Atkinson, Thorley; Cipriani, Chapman; Hohneck, Gleave, Balmain, Slater, Mostert (capt), Clarke, Ludlow, Ackermann.
Replacements: Walker, Rapava-Ruskin, Knight, Morgan, Hinkley, Varney, Evans, Seabrook.
Referee: Luke Pearce.