Terenure College were presented with the Ulster Bank League Division 1B trophy after finishing the season with a remarkable 100% record by beating Buccaneers at a sunny Lakelands Park.
Terenure, who were crowned champions last month, rounded off a brilliant title and promotion-winning campaign as they won their 18th and final league game 36-29.
Following this defeat, second-placed Buccaneers will need to regroup quickly as they face a crucial Division 1A promotion/relegation play-off with Ballynahinch.
Converted Jack Carty and Conor Finn tries got the Pirates off to a flying start, while Ian Hanly and Fergal Walsh crossed either side of two Carty penalties as 'Nure trailed 20-12 at the interval.
But four second half tries from John Dever, Kevin O'Neill, captain James O'Neill and John Bollard completed a breathtaking comeback as the champions finished off the season in style.
Outstanding Terenure back rower Robert Duke heaped praise on his team-mates and coaches after the game and said he is ready for life in Division 1A.
“I'm very fortunate to be involved with this great Terenure side,” said Duke, who has been shortlisted for the Ulster Bank League Division 1B Player of the Year award.
“Next season is going to be a big step up, but this is a young and hungry group of players and we feel we can cope with whatever comes our way.”
Apart from one-point victories at Blackrock College and Belfast Harlequins back in October, Terenure had gone through their whole league campaign relatively unscathed.
Buccaneers, meanwhile, had recovered from a near mid-season collapse by recording six wins on the trot which, with Corinthians' poor recent form, reignited their promotion challenge.
And last Saturday, the Athlone outfit secured second spot with a dramatic 24-23 home win over rivals UL Bohemians.
Buccs were aiming to spoil the homecoming party for the champions and in doing so, set themselves up nicely for their play-off tie.
When the teams last met at Dubarry Park before Christmas, 'Nure took advantage of the windy conditions in the first half before holding out in the second period to win 13-0.
This afternoon though, the weather was ideal for running rugby and it attracted a big crowd to Terenure's final home fixture.
But the home support was stunned into silence after just three minutes when out-half Carty went in under the posts and converted to give the visitors an early 7-0 lead.
The visitors then scored a second try in the 12th minute as powerful centre Finn shrugged off some weak tackling to cross the whitewash. Carty converted to make it 14-0.
After Carty missed a penalty, the hosts hit back with a converted try from full-back Hanly on 20 minutes after Dever was held up over the line moments earlier.
Carty kicked Buccaneers 17-7 ahead before 'Nure second row Walsh dived over in the far corner on the half hour to reduce the deficit to five points.
Despite Mark O'Neill's miscued conversion, James Blaney's men came storming back and showing their hunger for another score.
However, they were penalised on the stroke of half-time for indiscipline and punished by the boot of Carty whose long range penalty put the Pirates eight points clear.
The margin was extended to 11 points when Carty successfully kicked a difficult penalty with the aid of the right post minutes after the restart.
Terenure replied through lock Dever, who broke the line to go under the posts in the 50th minute. Out-half O'Neill easily converted to make it 23-19.
But a fourth Carty penalty, again going over off the upright, put Buccaneers back in front by seven points before 'Nure grabbed their bonus point try.
Scrum half Kevin O'Neill dived over in the corner on the hour to bring the hosts within two points of visitors before Carty took his personal tally to 24 points with another penalty goal.
The sides were level after 68 minutes though when 'Nure skipper James O'Neill crossed from close range.
Although Mark O'Neill missed the resulting conversion, he sent centre Bollard surging over the line on 73 minutes to put Terenure ahead for the first time in the match.
O'Neill added the extras this time as 'Nure completed their clean sweep of victories. Scenes of jubilation greeted the final whistle and the fireworks were set off after the newly-crowned champions received their league silverware.
Referee: Olly Hodges (IRFU)