But the South Yorkshire side went down fighting and a last-minute conversion by Dougie Flockhart, from Latu Makaafi’s 18th try of the season, secured his side a dramatic 34-32 victory in front of a record Championship crowd of over 16,000.
Just as Bristol had done at Castle Park a week earlier in the first leg, Knights fully deserved their win and but for a disappointing performance at home could have been celebrating top-flight rugby next season.
In scoring five tries against two, Knights more than justified their first ever appearance in a Championship final and will surely be a threat to everyone again next season.
Sadly, No 8 Ollie Stedman, who had a huge game in both attack and defence, is moving on to pastures new, as is Jon Phelan, but the outstanding Will Hurrell and the vast majority of the squad will still be there.
Despite dominating the first half both in terms of possession and territory, Knights came in at half-time trailing 16-10.
They had looked to be back in the game, after they had trailed 9-3 against the run of play on the night, when Hurrell crashed through two tackles on 38 minutes for a try converted by fly-half Declan Cusack to make it 10-9.
But no sooner had the cheers of the Doncaster fans died down than Bristol scrum-half Will Cliff charged down an attempted clearance kick by his opposite number Michael Heaney on the 22 to score a converted try to leave Knights 21 points adrift.
Knights had a try by Mat Clark controversially disallowed at the start of the second half for obstruction. Bristol rode their luck and extended their lead on the night to 25-10 with three further penalties.
But despite having to reshuffle after losing Cusack, Knights hit back with two superb tries by full-back Paul Jarvis and wing Tyson Lewis and a try from a tap by Stedman saw them regain the lead in the tie.
James Phillips steadied Bristol’s nerves with a 73rd minute try but Knights finished the stronger and Makaafi scored from a driving maul to level the scores, allowing Flockhart to convert for victory on the night.
Bristol: Arscott; Wallace, Tovey, Mosses, Lemi; Sheedy, Cliff; O’Connell, McMillan, Perenise, Evans, Glynn, Mama, Lam, Phillips. Replacements: Brooker,Traynor, Cortes,Sorenson, Robinson, Roberts,Morgan.
Doncaster Knights: Jarvis, Bulumakau, Clark, Hurrell, Lewis; Cusack, Heaney, List, Hunter, Quigley,Challinor,Phelan, Shaw, Hills,Stedman Replacements; Veikoso, Sproston, John, Young, Makaafi, Flockhart, Field.