Welsh Rugby Union president Dennis Gethin presented the trophy to Glantaf as they gained ample revenge over their nearest and most fierce rivals following an earlier two point defeat in the season.
Warburton, who was in London seeing a specialist about his injured shoulder, had been in the Whitchurch HS side that won the title in 2007. And it looked as though the side he inspired with a training session last week were on course for another victory when left wing Tom Morris nipped in to intercept a passing move and race 50 metres to the line for the opening try of the game.
That score, converted by outside half Glen Evans, came after 20 minutes, but five minutes later Glantaf centre Josh Bridson crossed on the right for a try which outside-half Geraint Llewellyn duly converted to leave the scores level at the break at 7-7.
Glantaf were looking to give long standing rugby manager Dai Williams the perfect send off into retirement and two second-half tries enabled them to do just that.
Llewellyn gave Glantaf the lead after 45 minutes when he burst over near the posts after good phase play and his conversion made it 14-7. That score sparked a major reaction from Whitchurch HS and the rest of the game turned into a running fest as both sets of players went for glory.
But Glantaf managed to get knee-injury victim Roberts to jump out of his seat on 67 minutes when Jake Conway crossed for the Welsh language school's third try to make the game safe and give Williams the perfect retirement present.
Scorers: Ysgol Glantaf: Tries: J Princeton, G Llewellyn, J Conway; Cons: G Llewellyn 2.
Whitchurch HS: Try: T Morris; Con: G Evans.