With so much at stake, a solid start was needed at Beacontree Leisure Centre and it was Enfield who took an early command of the game.
Charlie Briers caused problems for the south Londoners right from the first whistle – superbly winning the sprint before firing in a hat-trick of unanswered goals from 2m.
Beckenham responded from two six on fives, but Richard Waller found space in attack to make it 4-2 to Enfield at the end of the first.
Ultimately it was a two-goal lead that Enfield never let slip.
In the second, late arrival Andy Boorman took over in goal and apart from the on-fire Freddie Pearsons, Beckenham struggled to find a way through.
Enfield’s Rob Lucas slammed home from distance, before a powerful drive from Craig Snowdon saw him convert to make it 6-4 at the half.
A lively third quarter saw both teams score four, with man-of-the-match Briers adding two more, Lucas executing a pinpoint lob and Andy Rollé finding the far corner after swimming the length of the pool.
With their two-goal lead still in tact, Enfield controlled the final period thanks to further goals from Snowdon, Lucas and Rob Threadgold.
Beckenham scored three of their own, but it wasn’t enough as Enfield kept possession and ran out the clock to end up worthy 13-11 winners.
The victory sees Enfield promoted alongside Division 3 champions Watford 2nds and they will play in the third tier of the capital’s water polo pyramid next summer.
Enfield’s team in full: Andy Boorman, Andy Poore, Charlie Briers (5), Rob Threadgold (1), Richard Waller (1), Alex Waller, Andy Rollé (1), Craig Snowdon (2), Rob Lucas (3), Martin Ilievski & Tom Mendham.