Leeds, with a Challenge Cup final looming were not at their best but, inspired by McGuire and Keith Senior, pulled away from the Broncos convincingly.
The Broncos had no chance to get into their stride before giving Leeds a present of possession, from which they fashioned their first try. Feleti Mateo lost the ball and the Rhinos moved it from the scrum base, across field through McGuire with Marcus Bai scoring in the far corner.
London played some glorious stuff in response, eventually getting their reward when Jon Wells reached up to take Luke Dorn's pass above his head and touched down.
Two minutes later, Lee Hopkins swatted up Kevin Sinfield to race away from dummy-half and put Dorn over for the Broncos' second converted try.
Leeds were still lacking their usual fluency, but they capitalised on a scrappy passage of play for their second try, Sinfield picking up a loose ball and feeding Mark Calderwood.
London had two scrums near the Rhinos' line but failed to turn them into points. They were punished for that when Leeds worked the ball up field and Andrew Dunemann's pick up and Gareth Ellis' final pass sent Chris McKenna over by the flag.
Leeds' inability to kick any of their three conversions left the scores level, but they were ahead by half-time thanks to another scruffy try, Senior this time scooping up the loose ball and fending off a series of tackles.
Within a minute of the restart, McGuire had doubled that lead, sprinting 60-metres on an arcing run reminiscent of his most compelling form last year.
Three minutes after that, Rob Burrow got a clever one-handed pass to Senior, who scrambled over Broncos' bodies for his second with Burrow finally kicking a Leeds goal. London bounced back with Paul Sykes' try followed by his third goal, but that was as close as they could get.
Just past the hour mark, Senior stumbled through a couple of tackles but still managed to get his pass to the supporting McGuire and Leeds were on their way back to the summit.
McGuire backed up Ali Lauiti'iti to complete his hat-trick eight minutes from time before the excellent Senior sent him over again and the industrious Hopkins laid on a late second for Sykes.
Leeds: Mathers; Calderwood, Walker, Senior, Bai; McGuire, Dunemann; Bailey, Diskin, McDermott, Ellis, McKenna, Sinfield. Substitutes used: Burrow, Lauiti'iti, Scruton, L Smith.
London: Wells; Kirkpatrick, T Smith, Sykes, Bradley-Qalilawa; McLinden, Dorn; Trindall, Hopkins, Armour, Haumono, Mateo, Mbu. Substitutes used: Williams, Stephenson, Tookey, Highton.
Referee: R Silverwood (Mirfield)Reuse content