England winger Ryan Hall celebrated his new five-year contract with a hat-trick of tries as Leeds went top of Super League with a predictable demolition of winless London.
Hall, recalled after being rested for his side's win over Widnes, scored all his tries before half-time as the Rhinos cruised into a 34-0 lead in the mismatch that most observers feared.
Fellow winger Ben Jones-Bishop also got in on the act, scoring two tries for the second successive week, in Leeds' 54-6 triumph.
For the Broncos, who lost forward Atelea Vea with a damaged spleen on only his second appearance in Super League, it was damage limitation from the start, although they provided a glimmer of hope for the rest of the season with a spirited second-half performance.
Such was the foregone conclusion that Leeds' former London coach Brian McDermott felt able to rest skipper Kevin Sinfield - for the first time since 2009 - and his England team-mate Tom Briscoe.
The Rhinos boss, who was also without injured forwards Jamie Peacock and Brett Delaney and centre Joel Moon, opted to give a debut to 19-year-old prop Rob Mulhern as well as a second appearance to 18-year-old Elliot Minchella.
But there was still bags of experience, especially in the shape of half-backs Rob Burrow, who captained the side on his 350th Super League appearance, and Danny McGuire.
Slotting effortlessly into Sinfield's shoes, McGuire placed a pinpoint grubber kick to create the first try for Brad Singleton after just 84 seconds.
Hall, who made life a misery for his opposite number Jamie O'Callaghan, grabbed his first after only seven minutes, taking Stevie Ward's pass and fending off his man to touch down.
England's record-breaking winger then pounced on kicks from McGuire and Burrow to complete his hat-trick before half-time and second-rower Mitch Achurch proved unstoppable from 10 metres out after charging onto Paul Aiton's pass.
Leeds' best try came from right winger Jones-Bishop, who finished off a 70-metre move sparked by full-back Zak Hardaker, who converted all but one of his side's six tries to make it 34-0 at the break.
And it was Hardaker who got the scoreboard rolling in the second half, dummying his way over within three minutes of the restart and kicking his sixth goal.
London's youthful side, with an average age of 22, battled manfully against the odds but when second-rower Mike McMeeken breached the Leeds tryline he was unable to ground the ball.
However, the visitors' perseverance was rewarded on 49 minutes when centre Mason Caton-Brown found a gap in the Leeds defence to score his side's try, to which Josh Drinkwater added the goal.
Caton-Brown then scrambled superbly to deny Carl Ablett a try following a break down the middle by Burrow.
Watkins fluffed a chance by knocking on with the line at his mercy but he made amends on 57 minutes by slicing through the Broncos defence for Leeds' eighth try before carving out an opportunity for Jones-Bishop to add his second.
Burrow then marked his landmark appearance with a trademark burst to round off the scoring with his side's 10th try and also added the goal.