Four tries in the first half-hour from Danny McGuire took Leeds back into second place in Super League as they inflicted more home misery on a badly depleted Harlequins.
McGuire's exhibition of support play took his tally for the season to 11 - the best in the competition. Although he and his team-mates eased up visibly after half-time, they were still far too good for Quins, who have yet to find the form to justify their quest for a higher profile in the capital.
With eight regulars missing, it always looked set to be a night of struggle for the Londoners at a new home ground where they have yet to win.
Their problems started after 10 minutes. Richard Mathers split their defence with a dummy and McGuire was there in support. McGuire's second, three minutes later, was almost a carbon copy, with Rob Burrow making the break and his half-back partner again left with no one to beat. Kevin Sinfield kicked both goals.
The home side knuckled down a little after that, but they were opened up again in the 25th minute by Keith Senior bursting through a couple of ineffectual tackles. He found Lee Smith, who had the choice of McGuire and Burrow to pass to, and chose the latter.
Smith made it up to McGuire two minutes later, racing clear again and presenting him with his hat-trick. The exciting youngster then got free on the left yet again and there was McGuire once more - still without a man to beat as he went in for his fourth.
By way of variation, McGuire then turned provider to send Willie Poching over as Quins' ragged defence threatened to disintegrate completely.
With a 36-point lead in their pockets, Leeds lost some of their urgency after the break. They even came close to allowing Quins on to the scoresheet, when Smith's tackle took Nick Bradley-Qalilawa's foot into touch.
Smith, just 19 but so full of potential, got a richly deserved try when he intercepted Luke Dorn's pass, but Quins' improved tackling meant that clean breaks were harder to come by until the last 10 minutes, when Leeds ran in tries through Ali Lauitiiti, Chris Feather and Senior, the last from a clever pass by McGuire.
Harlequins: Dorn; Bradley-Qualilawa, Hartley, T Smith, Gafa; Weisner, Leuluai; Tookey, Randall, Lolohea, Mbu, Hopkins, Williams. Substitutes used: Budworth, Heckenberg, Mills, McCarthy-Scarsbrook.
Leeds: Mathers; Donald, Ellis, Senior, L Smith; McGuire, Burrow; Peacock, Diskin, Feather, Poching, Kirke, Sinfield. Substitutes used: Millard, Lauitiiti, Bailey, Scruton.
Referee: R Silverwood (Mirfield).
Sunday Best: Safety net in Tigers' hunt for survival
Castleford admit to being six points better off than they thought they might be at this stage of the season and can take another small step towards safety if they beat Huddersfield today.
The promoted Tigers took advantage of sub-standard performances by Catalans, Harlequins and Wigan. But they must do without Danny Sculthorpe for the next four weeks after he broke his thumb in last week's victory over Wigan, who loaned him out for the season.
They expect Ben Roarty to return against his old club. Craig Huby may be available after a broken finger. If he does not make it, 19-year-old second-rower Grant Edwards could make his debut after impressing for the Academy.
Cas are still searching for a half-back, although Ryan McGoldrick and Andy Kain showed good form in their last two games. It would have given them financial room to manoeuvre in that area if Keith Mason had gone on loan to Wigan this week, but St Helens, who loaned him to Cas, blocked that.Reuse content