Cavan summoned a dynamic display when cruising to an emphatic All Ireland football qualifiers round 1a success at Ruislip.
London were quietly confident of causing a surprise, but Terry Hyland's visitors were primed for a battle dictating this contest from the first whistle.
Inspired by Tomas Corr and Gearoid McKiernan Cavan dominated throughout against the typically spirited, but utterly outclassed Exiles.
Having come so close to nudging Monaghan out of the Ulster Championship a month ago Cavan responded to that defeat in splendid fashion.
With Corr smashing at centrefield Cavan's lively attack was provided was sufficient rations of possession to enjoy a productive opening period.
From 21 first half chances Cavan converted 11 points and the visitors could have added a couple of goals as London were fortunate to survive a few scares.
Corr and McKieran's excellence ensured corner forward Niall McDermott was able to contribute five points for Cavan before the interval.
Inside Michael Argue also provided a ball winning presence on the edge of the square as London were put under severe duress from the first whistle.
By the 17th minute Cavan had accumulated a 0-5 to 0-2 advantage as London were struggling to create scoring opportunities.
The Exiles' cause was scarcely aided by a black card brandished to Caoimhin Carty on the quarter hour mark.
Paul Coggins' side were honest and an Alan O'Hara point narrowed the gap to two before Cavan reeled off six points without reply.
McKiernan crafted space for McDermott to kick a beauty and that was followed by five more efforts from the vibrant visitors.
Dara McVeety, McKiernan, Martin Reilly (free), McDermott, and Corr all rifled over scores for a dominant Cavan side.
An O'Hara free for London ensured Cavan went in armed with a commanding 0-11 to 0-4 advantage at the break.
In the third quarter London enjoyed some small moments of encouragement as forward Lorcan Mulvey, a Cavan native, offered a genuine threat.
With substitute Liam Gavigan also impressing London trailed 0-14 to 0-7 before the match was held up for 10 minutes due to a leg injury suffered by Cavan full back Rory Dunne.
Following that stoppage Cavan replacement Cian Mackey nailed a gorgeous point before McKiernan returned to centre stage.
In the space of three action packed minutes McKieran contributed 1-3 on the spin including an opportunistic 57th minute show.
Argue's initial shot drew a fine reflex save from Declan Traynor, but McKiernan slammed the rebound home.
London were now merely keen to keep the scoreline respectable as Cavan continued to inflict further damage.
Argue was involved in a second goal which McVeety palmed to the back of the London net in the 64th minute.
At the opposite end Mulvey continued to drill over frees, but Cavan weren't too bothered as they easily closed out the deal.
In the 11 minutes of additional time London had Cathal Og Greene sent off for a second bookable offence as Cavan advanced with the minimum of fuss.
Scorers for Cavan: G McKiernan 1-6, D McVeety 1-2, N McDermott 0-5 (2fs), T Corr 0-3, N Murray 0-1, E Reilly 0-1, C Mackey 0-1, M McKeever 0-1, M Reilly 0-1 (f), R Galligan 0-1 (45).
Scorers for London: L Mulvey 0-6 (4fs), A O’Hara 0-3 (1f), D McGreevy 0-1, L Gavigan 0-1.
Cavan: R Galligan; J McLoughlin, R Dunne, K Clarke; C Brady, F Flanagan, D O’Reilly; T Corr, G McKiernan; D McVeety, N Murray, M Reilly; R Flanagan, M Argue, N McDermott. Subs: C Mackey for Clarke (11 mins), J McEnroe for Dunne (53 mins), E Reilly for Flanagan (60 mins), M McKeever for Brady (66 mins), P Smith for M Reilly (66 mins), K Brady for Murray (70 mins).
London: D Traynor; B Collins, P Butler, S Curran; M McCoy, C Carty, D McGreevy; M Carroll, A Bradley; S Conroy, M Gottsche, C Og Greene; A O'Hara, L Mulvey, A Moyles. Subs: N Boyle for Carty (16 mins, bc), L Gavigan for Moyles (33 mins), A Carr for O’Hara (46 mins), C Sheridan for Conroy (60 mins), A O’Regan for Bradley (65 mins), S Devine for McCoy (66 mins).
Referee: P Neilan (Roscommon).