Those who braved the bitter Ruislip cold were treated to a lively game which was decided by an Offaly scoring burst in the third quarter.
Paul Coggins’ London battled extremely well in the opening period and only trailed by 0-2 to 0-1 at the interval.
After the restart, though, Offaly improved significantly as six points on the spin from Declan Hogan, Bernard Allen (2), Padraig Sullivan, Nigel Dunne, and William Mulhall had them seven clear.
Alan O’Hara, impressive in attack for London, narrowed the gap and when Lorcan Mulvey converted a 64th minute penalty the gap was narrowed to three.
Offaly stayed cool under pressure as Allen nailed an insurance free and the Division Four promotion favourites departed the Emerald GAA Grounds with an encouraging success.
Scorers for Offaly: B Allen 0-3 (3fs), D Hogan 0-1, G Guilfoyle 0-1, P Sullivan 0-1, W Mulhall 0-1, N Dunne 0-1, R Allen 0-1.
Scorers for London: L Mulvey 1-0 (pen), A O’Hara 0-2.
Offaly: A Mulhall; D Brady, P McConway, J O'Connor; C Donohue, J Maloney, D Hogan; G Guilfoyle, R Allen; E Carroll, P Sullivan, N Bracken; B Allen, N Dunne, W Mulhall.
Subs: D Kelly for W Mulhall (53 mins), J Evans for Bracken (53 mins), N Smith for Carroll (55 mins), M Young for Sullivan (60 mins), N Darby for Hogan (63 mins).
London: B Kavanagh; D McCarthy, P Butler, P Galvin; C Og Greene, M Carroll, D McBride; M Gottsche, A Bradley; G Crowley, S Conroy, C Sheridan; A O'Hara, A Moyles, L Mulvey.
Subs: B Smith for Moyles (48 mins), M Walsh for McBride (52 mins), S Curran for Greene (55 mins), S Hickey for Conroy (60 mins).
Referee: G McCormack (Dublin).