Harlequins head coach McDermott jolts league leaders Leeds Rhinos

The former marine, who signed a new deal in midweek which will see him remain at the London club until 2011, had to field a weakened side due to injuries, but they dominated a pulsating encounter.

Lamont Bryan, of Harlequins, forces through the Leeds Rhinos defence

Two tries from Will Sharp and Rhinos' misfiring kicker Kevin Sinfield helped Quins to end a nine-game winning run by the World Club champions.

Rhinos' prop Jamie Peacock proved he had shaken off an arm injury by scoring after four minutes. Matt Diskin caught the Quins defence slumbering and fed the big man who touched down. But that early score only sharpened the Quins' resolve and 13 minutes later they were in front with converted tries from Sharp and Scott Hill.

The Rhinos thought they had levelled the game but Rob Burrow's try was disallowed for obstruction. To compound Leeds' woes, Henry Paul knocked over the resulting penalty to make the score 14-6.

Leeds did score again before the interval when Scott Donald went over having caught Burrow's miss-pass. Sinfield added the extras to make it 14-12 at the break.

Quins' Chad Randall wriggled over eight minutes after the restart as his team continued to out-muscle and out-think the visitors. Leeds pulled the score back to 20-16 when Keith Senior charged over but Sinfield crucially missed his conversion.

Rhinos frustrations began to show and a melee broke out with 14 minutes left on the clock. Senior was deemed to have initiated the scuffle and was sin-binned, as was Quins' Louie McCarthy-Scarsbrook.

Paul sent over the resulting penalty in a perfect kicking game. Sharp then scored his second try but Rhinos hit back immediately though Burrow.

From a similar angle to his earlier miss, Sinfield saw his effort bounce out from the other post. When Donald went over again with four minutes left, Sinfield fluffed his third kick and Quins held on.