Another tight-as-you-like encounter between these evenly-matched rivals delivered a breathtaking climax that sparked joy in the Jersey camp, both those at Castle Park and the hundreds if not thousands following on social media or via BBC Jersey.
Replacement Rory Jennings made his Jersey debut with just a few minutes remaining and his side trailing 19-17, and the 20-year-old loan signing from Bath set up Tua Otto for the winning try at the death. Jersey's 19-24 triumph was enough to secure the Islanders' place in the quarter-finals of the British & Irish Cup for the first time in four attempts. Doncaster's bonus point meant they also qualified as pool winners, but could not secure a home quarter final.
The first half was a cautious affair featuring just two scores, a penalty for each side. Jersey's scrum was in the ascendance but the visitors couldn't translate this factor into points on the board, apart from Brendan Cope's 18th-minute kick.
The Knights had a few chances to run from deep - a Dougie Flockhart kick ahead just eluded his chasing team-mates, and then Dec Cusack set up winger Tyson Lewis, who muffed the opportunity with a poor pass.
Jersey went into half-time with just 14 men after Otto was yellow-carded for interfering with Michael Heaney's quickly-tapped penalty when he hadn't retired 10 metres.
It wasn't long until the game opened up after the break, with scrum-half Michael Heaney going over after the ball was worked wide from a scrum and Andy Bulumakau went close.
Heaney might have scored again but his effort was ruled out due to Cusack having put a foot in touch before delivering the final pass, and although Flockhart added another three points from a penalty, Jersey were back to 15 men and back in contention when skipper Pierce Phillips crashed over after good handling from the Jersey pack.
Another penalty stretched Knights' lead to six points, but then Jersey took the lead for the first time with quarter of an hour to play, Gary Graham finishing off a powerful rolling maul and Cope adding the extras. Flockhart's fourth penalty restored his side's lead, but Jennings and Otto had the final word.
With 21 points, Jersey had the best record of any runner-up in the B&I group stages, and qualified for the quarter-finals along with London Welsh and Moseley, while Bristol and London Scottish missed out.
1. Leinster A - 29pts (top of pool 1) *
2. Yorkshire Carnegie - 26 (top of pool 3) *
3. Bedford Blues - 19 (top of pool 2) *
4. Cornish Pirates - 23 (top of pool 4) *
5. Doncaster - 22 (top of pool 5)
6. Jersey - 21 (2nd in pool 5)
7. London Welsh - 20 (2nd in pool 4)
8. Moseley - 20 (2nd in pool 1)
9. London Scottish - 19 (2nd in pool 3) #
10. Bristol - 19 (2nd in pool 2) #
* = home quarter-final # = eliminated
The quarter-final pairings will be confirmed by the Organising Committee during the first week of February. Games will take place over the weekend on Friday 11th to Sunday 13th of March. The semi-final draw will also take place at the start of February with games to be played on the weekend of Friday 18th to Sunday 20th of March.
A delighted Harvey Biljon said: "To go through is fantastic and to do it by beating a side who are second in the Championship is even better. You've got to give our players a huge amount of credit."
The only disappointment of a red-letter day for Jersey was the enforced cancellation of Jersey Athletic's match against Blackheath Heathens, with the Jersey squad unable to leave the Island after their flight was cancelled following adverse weather.
Doncaster Knights: Jarvis; Flockhart, Bulumakau, Clark, Lewis; Cusack (Humberstone 68), Heaney; List (Pasquali 68), Hunter (Veikoso 65), Quigley (Sprotson 68), Challinor, Hotson (Phelan 65), Maka'afi, Hills (c), Stedman (Shaw 65).
Jersey: Adair; Howe, Otto (YC 39), Cooke, Lane; Cope (Jennings 77), Fisilau (Moates 61); Lockwood (Lancuba 68), Selway (Garcia-Veiga 50), Tomaszczyk (Kerrod 46), Phillips (c), Rowlands (Kolo'ofa'i 61), Freeman (Rae 45), Graham, Haining.
Referee: Michael Hudson (RFU)
Try: Bulumakau 42
Conversion: Flockhart 42
Penalties: Flockhart 7, 49, 59, 70
Tries: Phillips 52, Graham 64, Otto 80
Conversions: Cope 52, 64, Jennings 80
Penalty: Cope 18
pictures by Verienne Belcher
Why not come a chillout in the supporters marquee before the game, A fully stocked bar and food is available, seated and standing tables, on a first come first served basis and a great place to meet the Reds supporters.