Wigan laboured to a third-straight victory to climb to within touching distance of the top-four.
But playing their fourth game in 14 days, they seemed to lack energy and this was hardly the performance which set pulses racing.
They trailed 8-6 at half-time and needed a fortuitous try from Chris Hankinson to poke in front.
Morgan Escare went over - during Wigan's brief purple patch - and they were able to keep their spirited opponents at jabbing distance away to cling on to the two points.
The win kept Wigan in eighth spot but - crucially - moved them to within just two points of the top-four ahead of other round 14 fixtures.
For London, this was a seventh league defeat.
But they battled until the end, they kicked well and if their handling had been better, they could have caused Wigan's defence more trouble.
With Joe Burgess nursing a knee injury, Morgan Escare was recalled to the wing spot. Dan Sarginson was still not fit to return, keeping Hankinson at centre, while Oliver Partington was squeezed out by the return of Romain Navarrete.
A Thursday night game against London - in front of the Sky Sports cameras - was never going to produce a crackling atmosphere, even if this was Wigan's last match at home for seven weeks.
Lam had said during the week he wanted to show supporters how far they had progressed since their shock 18-16 loss in the capital in February.
But by half-time, there was a gloomy sense of deja vu as the hosts took the lead and limited Wigan to a solitary try.
Too often, they lacked punch down the middle, and when they did get into London's territory their last-tackle options seemed to range from pedestrian to poor.
Kieran Dixon - who scored a game-changing stunning try in their previous meeting - struck a sixth-minute penalty to give London the lead.
Wigan briefly improved and in the 10th minute, they launched their first real attack but Zak Hardaker couldn't reel in George Williams' floated kick over.
They maintained the pressure, however, and Jake Shorrocks darted through a gap to slide over for the opening try. Hardaker's conversion gave them a 6-2 lead by the quarter-mark.
But the Broncos' response was immediate. Helped by Bullock's spill, they tested the Warriors' line before Abdull stabbed a kick through for Jay Pitts to ground.
The try was given the green-light by the video referee and Dixon's goal inched them 8-6 ahead.
Wigan still had plenty of time to retake the lead before the break but too often they looked frustrated and flustered, confused and clueless, and there were some boos from the stands as they made their way down the tunnel.
Could Lam's instructions transform their fortunes? When Sean O'Loughlin twice spilled early in the second-half, the omens didn't look good.
But from a scrum, Elliot Kear spilled a regulation pass and Hankinson scooped up the loose ball and dashed over. Hardaker's goal put Wigan in front for the first time.
They chalked up their third try before the hour with a stylish attack to the left ended with Williams dribbling the ball through for Escare to collect.
With Hardaker maintaining his perfect strike-rate, Wigan opened up a 10-point buffer - and they immediately went hunting more points.
They didn't get them, and with their discipline again piggybacking London down field, they had to scramble well to keep out Williams.
From there, the Warriors looked content to wind down the clock and it nearly came back to bite them when Dixon broke down the right, only for the move to break down.
They at least get a long turnaround before their next game, against Warrington in the Challenge Cup.
Wigan: Hardaker; Marshall, Hankinson, Gildart, Escare; Williams, Shorrocks; Flower, Leuluai, Bullock, Isa, Greenwood, Smithies. Subs: O'Loughlin, Powell, Tautai, Navarrete.
London: Walker; Dixon, Morgan, Kear, Williams; Smith, Abdull; Battye, Cunningham, Butler, Pitts, Lovell, Yates. Subs: Richards, Hindmarsh-Takyi, Pelissier, Adebiyi.
Referee: Robert Hicks
Warriors starman: Thomas Leuluai