This was London's second Nicky Rackard victory, adding to the inaugural title they secured in 2005.
Louth were the beaten finalists back then as well, and driven by that memory, as well as their status as unfavoured underdogs, they tested the credentials of their heavily fancied opponents until the final quarter.
It was a case of redemption for London, though, who like Donegal in the Lory Meagher Cup, had lost the previous two finals. Eamonn Phelan brought a lengthy career to a close after last year's decider, but he was back as manager this time to steer the Exiles over the line.
Finn and Louth's Diarmuid Murphy gave an exhibition of free-taking in the opening period, regularly slotting placed balls from around the 65-metre mark. Crucially, though, Finn struck for two goals that gave London a 2-7 to 0-7 lead at the break.
The first arrived in the 25th minute when the full-forward beat his man before sending a handpass across the area. Retreating Louth half-back Donagh O'Sullivan nipped in to divert it from the waiting Henry Vaughan but Finn was on hand to finish from close range.
He struck again 10 minutes later when taking a pass from Patrick Sloane to bring his own personal tally for the opening period to 2-5, with Murphy supplying five of Louth's points.
The scoreline was flattering to the winners but there was no doubting their superiority after the resumption.
Neither side made too many inroads at the beginning of the second half, but it was Canty's influence that was most notable as London eventually pulled away.
The former Cork senior hurler was only introduced in the 30th minute, losing his place after missing the semi-final due to a wedding in Ireland, but he scored five second-half points from play and was fouled for two more frees that were converted by Finn.
"It's great that we've finally done it," said Finn. "There's not as much hype as the last two years because, to be honest, it's a relief as much as anything.
"We've such a strong bunch of players and there are plenty of lads who've been training with us that didn't make the match-day squad. It's just brilliant."
Louth manager Paddy Kelly was proud of his players' efforts.
"Our lads are getting there. We played Wicklow last year in the (Division) 3B final and lost and they were in the Christy Ring final. So we're there or thereabouts. I think that London team would trouble a lot of teams in the Christy Ring."
Scorers -- London: M Finn 2-8 (6f, 1 '65), K Canty 0-5, S Ryan, M Walsh 0-2 each, R O'Connell, N Forde, J Mulcahy 0-1 each. Louth: D Murphy 0-8f, Diarmuid O'Sullivan, S Fennell, D Horan 0-1 each.
London -- A Ryan 7; T Hogan 7, B Costello 7, C Burke 7; M Walsh 8, C Forde 7, G Hill 6; E Cooney 6, K Bolger 7; R O'Connell 7, S Ryan 7, N Forde 7; P Sloane 7, M Finn 9, H Vaughan 6. Subs: K Canty 9 for Cooney (30), J Maher 6 for Vaughan (41), D Maher 6 for Hill (49), J Mulcahy 6 for Bolger (52), B Hassett for Sloane (64).
Louth -- E McArdle 8; M Wallace 7, C Kerrigan 6, A Wallace 6; D Horan 8, R Byrne 7, Donagh O'Sullivan 7; G Smyth 6, D Dunne 7; D Kettle 6, S Callan 6, D Murphy 7; B Corcoran 6, P Brennan 6, Diarmuid O'Sullivan 6. Subs: W Morrissey for Brennan (43), D O'Hanrahan for Smyth (55), S Fennell for Kettle (55), K McNally for Diarmuid O'Sullivan (58), K Walsh for Corcoran (62).
REF -- M Haverty (Galway)