The result does not change the competition places — Thistle remain second and United, third, with Napier team Port Hill out in front.
But it breathes life into the contest for local bragging rights.
Heavy Equipment Services Gisborne United are now only three points behind Gisborne Vehicle Testing Thistle, and the teams meet again, probably in September, to play Thistle's home game that was postponed in June because of sodden grounds.
In the meantime, United retain the Challenge Cup, which goes on the line every time the holders play a home league game.
United opened the scoring in the 33rd minute, when left-winger Malcolm Marfell's inswinging corner from the right beat everyone and landed at the feet of leftback Dane Thompson, who tapped it in at the far post . . . 1-0.
Less than two minutes after halftime, a long ball out of United's defence caught the Thistle rearguard on the hop . . . the first man in was wrongfooted by the flight of the ball and that left Daniel Venema to deal with perhaps the fastest striker in the league. Josh Adams won the race and poked the ball past goalkeeper Mark Baple with the outside of his left foot . . . 2-0.
For the next five minutes, Thistle looked a beaten team, but they pulled themselves together and had the better of the second half as they pressed to get back into the game.
In the 57th minute, right flank midfielder Brandon Josling got to the byline and crossed to the edge of the goal area. United keeper Seth Piper dived out full-length to palm the ball clear, as far as Thistle skipper and central midfielder Nick Land. His first-time sidefooted strike from 12 metres gave his side hope at 2-1.
The rest of the second half was end-to-end action as the Jags tried everything to pierce a committed United rearguard.
Thistle looked at their most vulnerable when United gave themselves breathing space with long clearances down the middle.
Thistle coach Garrett Blair had changed from a three-man to a four-man defensive line at halftime to counter the threat of United wingbacks Dane Thompson and Mal Scammell. That part of the plan worked, and United had to fall back in numbers to repel the attacks that sprang from Thistle fullbacks Emerson Araya on the right and Kuba Jerabek on the left.
But it exposed Thistle to another danger.
Double centrebacks usually cover each other, unless one is a designated sweeper. When the ball is played in from the wing, the far defenders cover the players closer to the ball. But when the ball is straight out in front and the line of cover less obvious, centrebacks can be caught square by the ball lofted over the top before fullbacks can get around to cover.
As United came under sustained attack in the second half, “clear it” became a more urgent sentiment than “play out from the back”. Almost by accident, United found they could turn desperate defence into promising attack with one kick.
Several times Thistle got out of some dangerous situations by good scrambling defence, or swift intervention by keeper Baple, but with a striker as fast as Josh Adams the danger is ever-present.
In the 88th minute, Adams got clear on the left. Venema valiantly gave chase, and Adams looked to have gone too far wide when he let rip with his left foot. Baple seemed to have it covered, and got a hand to it, and in the next instant the ball was swirling in the back of the net.
By now, Thistle were attacking by instinct. Striker Davie Ure, who spent most of the afternoon outnumbered by defenders, turned deftly in the penalty area and was just beaten to the ball by a clearing boot.
And then it was over.
United coach Corey Adams said it was “the best footy” he'd seen from his team in a long time.
“Everyone stood up today,” he said.
“It came down to who wanted it more, and we get to keep the Challenge Cup.
“Our back line seemed solid . . . they (Thistle) didn't have a lot of chances.
“I'm so happy with everyone. I'm a happy coach.”
Thistle coach Garrett Blair said he wanted to make sure his side won the midfield battle.
“For most of it, we did well, and we were unfortunate to concede,” he said.
At halftime he took off midfielders Ashley McMillan and Agustin Ventre and put on fullbacks Araya and Jerabek. He changed the first-half 3-5-2 formation to 4-4-2 (Ema Martos moved from right centreback into central midfield).
“We wanted a bit more stability at the back, and Dane Thompson and Mal Scammell were getting too much space,” he said.
“We changed to 4-4-2. That got us going in the second half and we were unlucky not to come away with more than one goal.
“They used the long ball well and we got caught a bit trying to press too high.”
Blair said Thistle's play in the second half had been “fantastic” and he thought he should have gone to 4-4-2 a bit earlier.
“If we had played 4-4-2 in the first 45 minutes, it might have been a different game.
“We have one more chance to have a crack at them, at home.”