Chris McDonnell (left) tries to burst away from Down's Liam Clarke
Down overcame a spirited London team to book their place in the Ulster Senior Hurling Final.
Gareth Johnson hit Down's first goal in the opening minute but London's Martin Finn hammered a 20-metre free to the net on 10 minutes to level the game.
After leading 1-9 to 1-6 at half-time, Brendan McGourty blasted in a 36th-minute goal for Down.
Paul Braniff's goal extended Down's lead and the talented forward struck another three-pointer late in the game.
Braniff finished with 2-4 for the winners while Martin Finn was London's top scorer.
Johnson's early goal came when he turned in Simon Wilson's delivery into the net.
However, Finn's goal for London brought the sides level at 1-2 apiece.
The sides were still level at 1-6 each but scores from McGourty, Wilson and Emmett Trainor helped the Mourne County lead by three at the interval.
McGourty's goal came a minute after the restart and Braniff struck his first goal on 45 minutes.
Braniff's second goal came five minutes from time.
Down: Graham Clarke; L Clarke, S Murray, F Conway, S Wilson, K Courtney, Gabriel Clarke; A Savage, R McGrattan; P Braniff, B McGourty; C Woods, E Clarke, G Johnson, P Coulter.
London: G McCollum, P Mulcahy, S McLoughlin, T Simms, T Abernethy, N Healy, E Phelan, F McMahon, C O'Halloran, J McCarthy, S Quinn, M Mythen, K McMullan, M Finn, C McDonnell.