The first words Jason Swain could muster in a touching embrace with Canberra Royals coach Wayne Southwell stand as a worthy testament to his mentor.

Nobody else would be able to lure the Royals outside centre back. Not after he stood in the clubhouse at Phillip Oval on this day last year, telling everyone he was happy in retirement.

He had walked away on top after an unbeaten season in 2017. As much as it hurt to watch his former teammates drop last year's grand final, he certainly didn't miss waking up sore every Sunday.

But for "Southy"? The pain seemed worth going around for one more year. And the moment he lifted his daughter Spencer towards the sky at full-time, Swain knew it had all been worth it.

Swain scored two tries to help lift Royals to another John I Dent Cup triumph in a thrilling 32-31 triumph over the Tuggeranong Vikings at Viking Park on Saturday.

"I really wouldn't do it for anyone else, the feeling he puts behind the team, and that family feeling, it's so big for the club," Swain said.

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"It's an amazing feeling. Doing it with those boys, it's really like a good community feeling about the place. Everyone just dug deep and did it for each other.

"He actually cares about the players. He does all the research and makes sure we know what we're doing, he makes sure we're fixing out mistakes at training. He knows how you're feeling."

His man of the match performance - to which a stunned Swain said "no shit?" in disbelief, coupled with the thrilling finale, were a script writer's dream.

For it seemed Tuggeranong had one hand on back-to-back titles before Swain and Andy Muirhead each scored tries in the space of two minutes to take back the ascendancy.

Royals scrumhalf Pedro Rolando was made to wait before he could line up the conversion which would ultimately prove the difference as Tuggeranong's Billy Carberry was taken from the field in an ambulance following a heavy collision.

When he got his chance after a 10-minute delay, he took it - and Royals were ahead by eight with little more than two minutes to play. But only the uninitiated could count out Tuggeranong in such circumstances.

Maika Ravouvou soon crashed over and the margin was back to one when Rolando fed a scrum with the clock at zero.

Vikings would scrap to win the ball back before Luke Gersekowski put a kick through a gaping hole for Joe Langtry - but he was bundled into touch by Royals veteran Craig McMahon to secure Royals a third title in five seasons.

That feeling will never get old for Southwell, nor does the impact of a player like Swain.

The Royals coach knew he had brought the outside back into the fold again for a reason. He and Muirhead combined with the competition's player of the year in Rolando to execute the perfect comeback victory.

"He is a big game player, he just saves his best until last. To see him at his peak again is something to behold," Southwell said.

Rest assured that will be his last.

"We're not doing it just for the glory, we're doing it for everyone on the hill," Swain said.

"That's it for me now."

There is no better way to finish, for the Royals reign in Canberra once more.

AT A GLANCE

John I Dent Cup grand final: CANBERRA ROYALS 32 (Jason Swain 2, Andy Muirhead, Ben Johnston tries; Pedro Rolando 3 cons; Pedro Rolando 2 pens) bt TUGGERANONG VIKINGS 31 (Maika Ravouvou 2, Lachlan Lonergan 2, Sione Taula tries; Ryan Lonergan 4 cons; Ryan Lonergan pen) at Viking Park.