A bumper crowd saw Gainsborough secure their National League North status, despite losing 1-0, as results elsewhere went in their favour.
Trinity’s fellow relegation threatened side Brackley had to win away at Curzon Ashton, but they could only draw in Greater Manchester.
It was an afternoon of a whole range of emotions at the Martin and Co Arena, where a Jerome Wright drive just after the break won it for FC United.
It had looked like only two points would separate the Blues and Brackley going into the last round of fixtures next Saturday, with Brackley a goal up on Curzon with seven minutes to play.
Other sides in and around Gainsborough were winning too to make matters worse.
Fortunately it all worked out for the Blues, overall, even if in their own match they paid the price for not putting the ball in the net.