London Broncos coach Tony Rea predicted the battling 21-14 triumph over St Helens could help turn around his club's season.
Rea's Londoners earned a first home win over Saints since 2002 and a first Stoop success of the Super League campaign, which also ended a run of 13 straight wins for the visitors in London.
After withstanding some early pressure, a St Helens side missing a host of stars struck twice within five minutes with tries from Anthony Laffranchi and Adam Swift.
But London, who only had 17 fit players themselves, struck back with a Chris Bailey try, then further scores early in the second half through Michael Robertson and Tommy Lee.
Paul Wellens ensured a nervy close when he crossed with 12 minutes remaining, only for Michael Witt to kick both a penalty and drop-goal in the closing seconds to seal the win.
Rea said: "It is a very important win for us. We had to make sure we came away with the two points.
"In this game you take it week-by-week, getting two points this week and then the next, and then suddenly the whole direction of the team changes.
"I thought our control of the game was key today. We did not make an error in the last half-hour and that allowed us to defend well and see the game out."
Saints coach Nathan Brown said: "We created enough chances to win the game, but our decision making in key areas was not what we wanted it to be.
"We competed hard and there was nothing wrong with our energy levels. We had a lot of players playing out of position and at the moment we are feeling the pain.
"But there will be the long-term benefits to come as these young players are getting the experience that they need.
"We have to make sure we are turning these close losses into close wins and take it from there."