Spittle’s late try sealed an impressive comeback from the visitors, who had made life hard for themselves when they initially went 15-0 down, the hosts going on to enjoy an 18-3 advantage at the break.
Ampthill got on the board with an early, fifth-minute penalty from fly-half Russell Bennett before Knights’ Sam Olver levelled 10 minutes later.
The home side then scored two unconverted tries before the break, the first coming in the 23rd minute from Austin Wallis, although Bennett missed the conversion. Nine minutes later, Ampthill got themselves 13-3 ahead, Bennett missing the conversion again after Charles Beckett had got himself over the line.
Bennett had chance to make amends when Billy Harding went over in the 35th minute to make it 18-3, but again, he was unable to convert, misses that came back to haunt the home side late on.
After the break, Doncaster begin to assert more control.
Moments after arriving on the pitch, Billy McBryde placed an inch-perfect kick into Ampthill’s 22, setting the Knights up for a tap and go which Josh Peters was only too happy to benefit from – barrelling over for the five points, although Olver couldn’t nail the conversion.
After being handed two yellow cards in quick succession – for Harry Seward and Carl Burgess – Ampthill were soon under more pressure from a Knights attack that sensed the tide was turning.
Great work from the lineout allowed for quick ball to be given to Mark Best, who ran the try in unchallenged, quickly followed by the conversion from Olver, making it a three-point game.
The Knights then produced a magic moment to seal a memorable triumph.
AS the clock ticked down, from defending a lineout on their five metre line, Spittle burst clear and raced down the line for a match-winning score to leave the hosts stunned.
Ampthill XV: J L Smith; Goodchild, Hudson, Hartley, Skelcey; Bennett, Barrett; Crean, Harding, Lutui, Beckett (c), Jones, Arthur, Wallis, Monks. Replacements: Dickinson, Thornton, Seward, Burgess, Stonham, Fenley, Sharp, Dunn.
Doncaster Knights: Davey, Evans, Strachan, Best, Spittle, Olver, Dolly, Cade, Edgson, Denman, Drake, Peters, Davies, Graham (C), Volpi. Replacements: Roberts, Vaughan, Foster, Kelly, Hudson, Green, Margetts, McBryde.