Going into the wind for the second stanza, Collegiate never quit trying. St Paul's scored again in the 65th minute, but Whanganui got a reply converted try to winger Jack Evans under the posts, which O'Leary converted.
Coach Steve Simpson hoped that meant his team would win the second half 7-5, but play went deep into injury time for St Paul's to cross again and blow out the score.
"A lot of gutted boys today," said Simpson, who had been hoping to become the first coach to win a CNI title with two different schools, with Collegiate having had finishes of second, third and second in the last three years.
"The boys gave everything last week. It was almost our final, beating the best team.
"[St Paul's] played very well, they've just got threats all over the park."
Collegiate missed too many first-up tackles - St Paul's hitting up the middle and then whipping the ball wide.
Still, it could be said the 2021 team had overachieved, as the 2019 team was very strong, while the 2020 side had been led by NZ Schoolboy and Barbarians players Harry Godfrey and Adam Lennox in the halves.
"The hardest thing is to replace them," said Simpson.
"Shaun O'Leary at first five was really a second five, but he did a great job.
"The forward pack had hardly changed from last year. The backs have always been under pressure."
After two seasons of relative injury-free campaigns, Collegiate also lost fullback Luke Meyers for the season after being injured playing sevens, while midfielder Waqa Waqaicece broke his hand during the Quadrangular and received medical advice not to play for another four weeks.
No 8 Josefa Namosimalua was battling a shoulder injury and came off during the final.
In a slight correction from the preview story, CNI started in 2012 with Lindisfarne College the inaugural champions, followed by Francis Douglas Memorial College under Simpson the following year, before St Paul's started their dominant run, except for Wesley College winning 2017.
The AGM for the competition was to be held yesterday and Simpson remains in support of having finals day held at the neutral ground of Taupō's Owen Delany Park - an innovation that was brought in last year due to a shortened competition being split into two pools because of Covid-19 delays.
Collegiate have one more game this season and it will be a cracker – the derby with Whanganui High School 1st XV, current MRU Premier 2 table leaders, on Wednesday at 2.30pm.
St Paul's Collegiate 33 (J Broomfield 2, T Robb, A Paenga-Morgan, M Wrampling-Alec tries; J Williams-Wilson 4 con) bt Whanganui Collegiate 10 (J Evans try: S O'Leary pen, con). HT: 21-3.
Around the grounds
MĀORI VS PASIFIKA: Whanganui Pasifika won the battle of the cultural teams with a 51-17 victory over Whanganui Māori at Spriggens Park on Saturday. In an open and unstructured style of match, fitting the occasion, Māori had a small squad and dropped off a few too many tackles. They will now have a break until October when a squad will go to the Te Tini a Maui tournament on the East Coast. Pasifika will play Manawatu Pasifika this coming Saturday.
DIVISION 1: WRFU Division 1 has a new champion as Ruapehu Under 13 held off Marist Vikings U13 to win a 22-20 thriller at Spriggens Park on Saturday morning. Both sides went try-for-try, with Ruapehu getting the go-ahead score with around 10 minutes to go and holding on to the finish. Saturday was the finish for all WRFU junior grades.
SCHOOLBOYS: MRU Premier 2 leaders Whanganui High School 1st XV continued their momentum with a tough 27-11 away win over Feilding High 2nd XV on Saturday. Second on the table, City College 1st XV were scheduled to host Palmerston North Boys' High 3rd XV.
SCHOOLGIRLS: Whanganui High School and Cullinane College will face off in the final of the Whanganui Girls 10-a-side competition this Thursday. The two strongest schools, who also play in the MRU competition during the week, WHS and Cullinane accounted for Ruapehu College and Whanganui Girls' College respectively in the semifinals on Thursday. Cullinane are defending champions.