In a feisty encounter that had twists and turns throughout, Vale scampered two runs in the fading light to clinch victory by two wickets, with just four balls of the match remaining.
It was a magnificent triumph against a Brondesbury side who were top of the table coming into the fixture and had recorded three successive resounding victories in the league - but Vale were wonderful in the field and resilient with the bat to scramble across the finish line.
The match had been reduced to 30 overs a-side due to overnight rain, and Vale were at their spirited best with the ball from the outset. Josh Stevens, on debut for the senior side, grabbed the first wicket as he produced a hostile and controlled opening spell - and backed up by flawless ground fielding, Vale never allowed Brondesbury to stamp their authority on proceedings.
Steven Allweis entered the fray to maintain pressure and he picked up two wickets in two balls to establish Vale's dominance. Spin twins Ben Lederman and Toby Michaels stifled the opposition in the middle overs, before Lederman opened his account thanks to a smart stumping from Alex Haffner.
Allweis returned at the death to claim his third victim of the innings, and Vale went in at the halfway stage content with their efforts as they restricted Brondesbury to 129-5 off their allotted 30 overs.
On a tough pitch, the chase was never likely to be simple - but Vale were two wickets down within five overs and the target appeared a long way off. Adam Brand and Ben Lederman then came together and turned the tide on Brondesbury, putting the opposition under pressure with a series of boundaries.
Brand was controversially given out caught-and-bowled, despite strong suggestions the ball had not carried, but Lederman was unfazed - smashing a quartet of fours and a monstrous six to push Vale closer.
His dismissal shortly afterwards, and that of Ben Kohler, who was adjudged run out despite appearing to be safely home, sparked a middle-order collapse as Vale slumped from 81-3 to 87-7.
With hopes fading and Brondesbury increasingly optimistic, Vale required a substantial partnership and that arrived just in the nick of time from Neil Lederman and Josh Stevens. The pair played sensibly to guide Vale to within ten runs of victory, but Lederman was caught and the match twisted once more.
Stevens and Allweis survived a couple of run out opportunities to eke out valuable runs, and it was left to captain Allweis to strike the winning runs in the final over to push Vale over the line and spark jubilant scenes.
Stevens finished unbeaten on 17 as he belied his youthful age with a mature innings - and Vale were understandably elated with the result, one that leaves them just one win from safety.
BRONDESBURY 129-5 (30 overs)
VALE BOWLING
Josh Stevens 6-1-26-1
Neil Lederman 6-1-24-0
Steven Allweis 6-0-24-3
Benjamin Lederman 6-017-1
Toby Michaels 4-0-22-0
Adam Brand 2-0-12-0
VALE BATTING
Adam Spooner 7 ct
Ian Selby ct 0
Adam Brand 18 ct
Benjamin Lederman 29 ct
Ben Kohler 19 run out
Alex Haffner 1 ct
Jonathan Gould 3 ct
Neil Lederman 14 ct
Josh Stevens 17 not out
Steven Allweis 3 not out
Toby Michaels DNB