Featherstone’s top-four bid suffered a setback with their third home defeat of the season.
They were outplayed by resurgent London who continued their winning start under new head coach Andrew Henderson with their first away victory of the campaign. Players from both sides had difficulty holding onto the ball and staying on their feet in the slippy conditions
Alex Foster went close for Rovers, but an excellent attacking position was wasted when Paul Wood lost the ball close to the line.
London then came far more into the game and Rhys Williams was halted short before Brad Dwyer put them ahead after 23 minutes when he darted over from acting half for a try that Wes Naiqama goaled.
Rovers put their game together towards the end of the half.
They cut the gap to two points when Wood sent in young substitute Jack Ormondroyd after 33 minutes. Sykes’s attempted conversion struck a post and he was off target with a penalty kick on the stroke of half-time.
The Broncos increased their lead to eight points early in the second-half through Oscar Thomas with Naiqama converting.
Rovers looked rattled and their handling often let them down.
They fell further behind in the 58th minute when swift handling put in Rhys Williams.
Williams sealed London’s win when he raced 75 yards for his second try five minutes from time and Naiqama kicked his third goal.
Nathan Chappell’s late try was in vain for Rovers.
Featherstone Rovers: Hitchcox; Blackmore, Hardman, Chappell, Sharp; Sykes, Marginet; Baldwinson, Irwin, Bostock, Cording, Foster, Spears. Substitutes: Milner, James, Wood, Ormondroyd.
London Broncos: Hellewell; R Williams, Farrar, Naiqama, Macani; Thomas, Keyes; Lovegrove, Dwyer, D Williams, Harrison, Garside, Minchella. Substitutes: Nasso, Thackray, Dollapi, Everett.
Referee: M Woodhead.