The Eagles soared to victory, courtesy of a brace from Jemal McKenzie-Lowe in the 37th and then five minutes into stoppage time at the end of the game after Dan Gleeson had equalised on 66 minutes.
With second-placed Farnborough and now third-placed Barton Rovers and fourth-placed Marlow assured of their play-off places, the final spot is between current occupants Egham Town, AFC Dunstable or Kempston Rovers.
Barton ensured their extra games by beating the Walnut Boys of Kempston by the odd goal in five at Sharpenhoe Road, thanks to a Connor Calcutt brace, sandwiched by a Jimmy Hartley effort – Ashley Fuller bagging both of the visitors` goals including a penalty.
Marlow were 1-0 home winners over Chalfont St Peter, with Nathan Poulton`s goal four minutes into time added on at the end of the game proving decisive.
AFC Dunstable won 2-0 at Creasey Park against Aylesbury FC with Jermaine Hall after 12 minutes and BJ Christie 13 minutes from time the men on the mark.
Egham won 2-1 at Holloways Park against Beaconsfield SYCOB, whose Jack Lyons gave them a 26th minute lead that Elliott Carey after 36 minutes and Brendan Matthew`s 62nd minute spot-kick overhauled.
Northwood escaped the drop, despite going down 2-0 at neighbouring Hanwell Town, for whom Dean Allen and Callum Wright were on target.
Elsewhere, Farnborough lost 1-0 at Ashford Town (Middx), whose Jack Beadle scored the only goal on 66 minutes, while Josh Harfield and Mitch Parker scored to give Fleet Town a 2-0 verdict at home to doomed Petersfield Town.
Jon-Jo Bates bagged a brace to help Uxbridge to a best-of-five win at Potters Bar Town, for whom Ashley Nathaniel-George was also a two-goal man, and Sonny French and a Sam Warrell own goal helped Aylesbury United come back from being a 40th minute Tom Franklin goal down to Kidlington.
And champions Royston Town suffered only their fourth defeat of the season in a nine-goal thriller at Arlesey Town.
Jack Vasey bagged two for the hosts and Ryan Ingrey did likewise for the title-winners.
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