The upshot of this result, with Belvedere securing a losing bonus point, is that Clontarf top the table but only on points difference. They have, though, a match in hand over their south Dublin rivals and that could be crucial.
However, if they win their remaining three matches, even without a bonus point, it will be enough to secure that prized first national title.
The first chance fell to try-scoring machine Michael McGrath after 15 minutes when the winger broke from his own half, only being denied by desperate late tackle.
A minute later, Clontarf found themselves behind by five, Belvedere winger Phil O’Dwyer finishing an excellent move with a chip-and-chase try.
Declan Fitzpatrick nabbed an equalising try on 20 minutes, but Clontarf were caught napping immediately when they conceded a minute later, with Josh Glynn being credited with the score to secure a 10-5 lead for his side. Clontarf were rattled but they hit back before half-time with a penalty from out-half David Joyce to cut the gap to two.
The drama continued in the second half.
There were some magnificent cameo moments, mistakes seized upon, opportunities scorned, and with both sides seeking to play decent football it turned out to be a very good game.
As Clontarf turned the screw it got harder and harder for Belvedere and the winners went for the jugular, kicking to touch and mauling over for a try from hooker Brian Byrne which out-half David Joyce converted for a 15-10 lead.
Granted, Belvedere hit back with a penalty from Josh Glynn, but Clontarf struck back for a third — unconverted — try from Ian Hirst to secure a 20-13 advantage and they held that to the finish despite a quite magnificent late rally from Belvedere.
CLONTARF: D Fitzpatrick, M McGrath, C O’Shea, E Ryan, M McFarland, D Joyce, S Cronin, I Hirst, B Byrne, R Burke-Flynn, B Reilly, C O’Keeffe, K Moran, T Ryan, L Murphy.
Rolling replacements: C Culleton, T Byrne, K Donohue, P Du Toit, K Lett.
OLD BELVEDERE: J Glynn, A Wynne, J Kennedy, P Robb, P O’Dwyer, S Crosbie, A Sheehan, P O’Regan, K O’Neill, D Lavery, J E Whatiri, D Moore, J Slattery, J Conan, K O’Gormon.
Rolling replacements: A Harvard, B Coyle, L Auva’a, F Lawlor, S Berne.
Referee: L Colgan (IRFU).