Clonmel who have been threatening to become a force in Junior Rugby in recent years eventually stepped into the winners' enclosure to win the clubs first Munster trophy in front of a very large crowd.
Clanwilliam were well up for this tie and kept battling to the finish, but it is tries that win matches and Clonmel scored four as the Tipperary Town side failed to cross the white wash.
Clanwilliam were rocked on their heels as early as the second minute when a break by Clonmel's wing forward Frankie Quinlan set up a try for full back Conor Cooney in the corner.
David Kinehan and Kieran Merrigan were putting in big hits for Clanwilliam as Clonmel threatened to run rampant.
Gradually the Clanwilliam pack began to get on top winning turn over ball in the rucks.
Brian Kissane kicked two long range penalties on 9 and 13 minutes to put Clanwilliam 6-5 ahead.
The Second Division side were now full of confidence as they spread the ball around and looked the hungrier side. A great break by out half Kinehan saw him chip over the Clonmel defence but the ball went dead before he won the race to ground it.
Then disaster struck again for Clanwilliam a quick break up the blind side by Morgan Lyons and Greg Carroll sent Brian Smith in for a second try for Clonmel.
Kissane reduced the deficit with his third long range effort on twenty nine minutes, but Kissane elected to kick for touch when presented with another long range penalty just before half time.
The strong wind that blew across the pitch saw Clonmel elect to keep things tight in the forwards for the second half as Ronan Crosse began to win Clanwilliam ball at the line out. The First Division side began to dominate the game and had Clanwilliam pinned back in their own Twenty Two.
Clonmel extended their advantage on fifty four minutes when a break by Cooney and Luke Hogan saw his chip ahead being kicked away by the Clanwilliam defence but winger Greg Carroll was up to touch down and Cooney converted the extras.
Cooney made it 20-9 with a penalty on sixty minutes.
With time slipping away Clanwilliam rallied in the final ten minutes and had Clonmel camped in their own Twenty Two. Yellow cards to Frankie Quinlan and Neville Melbourne saw Clonmel reduced to thirteen and despite several scrums close to the Clonmel line following a series of penalties, Clonmel managed to kick the ball out of defence and Luke Hogan gathered the ball on his own Twenty Two and raced the length of the field to score and Cooney's conversion brought the game to a finish as the Trophy headed for South Tipperary for the next twelve months.
Clonmel: Conor Cooney; Greg Carroll, Luke Hogan, Brian Smith, David Lonergan; Morgan Lyons, Alex Sheehan; Mike Sheehan, Gareth Mulcahy, Mark Corby; Ronan Crosse, John Long; John Gallaher, Frankie Quinlan, Neville Melbourne.
Replacements: Padraig Keating, Brian Lonergan, Tony Cantwell, Stephen Pyke, Dylan Cadogan.
Clanwilliam: Robert Doyle; Gavin Ryan, Kieran Merrigan, Richard Childs, Pauric Ryan; David Kinehan, Derek Shiels; Jonathan Whelan, Ian O'Rahelly, Denis O'Brien; Brian Kissane, Paul Ryan; Ray Merrigan, Christopher Doyle, David McCormack.
Replacements: Brendan Quinlan, Eddie Ryan, John Richardson, Kieran O'Donnell, Vivion Grisewood.
Referee: Andy Brace (MAR).