Derry 1-13 London 0-10: Derry moved to within touching distance of safety courtesy of a fortuitous goal from Ruairi Convery that helped fend off London.
Derry, fresh from their shock win in Westmeath last weekend, started the brighter against the breeze and led by 0-5 to 0-1 after 22 minutes.
Ruairi Convery was posing problems for London when he got the right supply at full-forward, hitting three of his side's first half points.
The Exiles rallied in the final 10 minutes of the half, with Martin Duggan impressing when he moved out to centre-forward, and they dragged themselves level, though goalkeeper John Grealish could only register a point from a penalty during the revival.
But their chances were dealt a major blow on the stroke of half-time when Stephen Frawley was sent off for an off-the-ball strike on Ruairi Convery.
The Swatragh forward's goal came when Grealish spilled his 70 yard free into the net after 58 minutes, opening a five-point gap that London couldn't close, despite the best efforts of Lambert.
Derry: D McDermott; M Warnock, S McCullagh, N Farren; R McCloskey, L Hinphey, K Hinphey; O McCloskey (0-1), S McCloskey; B Rogers (0-2), T McCloskey, A Grant; P Cleary, R Convery (1-7, 1-5f, 0-1 65'), A Kelly
Subs: J O'Dwyer (0-2) for Cleary (HT), C Convery (0-1) for Kelly (HT), C McQuillan for Farren (55), P McCloskey for S McCloskey (55), M O'Hagan for Grant (65)
London: J Grealish (0-1pen); C McAlinden, C Smith, C Hickey; E Cooney, B Regan, S Frawley; D Moore (0-1), PJ Rowe; S Lambert (0-7, 0-3f), E Kelly, M Holohan; H Vaughan, M Duggan (0-1), L Hands. Subs: R Foy for Holohan (HT), K Coen for Kelly (HT), P Murphy for Vaughan (69), M Coen for Rowe (69), M Lynch for Hands (69)
Referee: O Elliott (Antrim).