It was a close call as Glenstal survived a hair-raising first 10 minutes to establish a match-winning 13-point lead at half time.
Thereafter, Glenstal had to pull out some stops against a Christians side that refused to lie down and looked to be on the cusp of restoring order when they pulled back 10 points with nine minutes plus injury time left on the clock.
It said much for Glenstal’s fighting spirit, however, that they managed to ride out the storm with a series of late attacks that yielded two kickable penalties, one of which was converted to give them the breathing space to hold on for a sensational triumph.
Christians had their opportunities, particularly in the early stages when number eight Evan Mintern, Kevin Creedon, Tomás Quinlan, Shane McAuliffe and James Bradfield led the charge.
But after an opening onslaught from Christians, the game settled into a much more even pattern.
Glenstal showed they weren’t to be trifled with when the launched their first assault in 10 minutes from which they took the lead.
Number eight Jack Boland broke from a scrum deep inside his own half and made huge yardage in a move that also involved Hugh Connors.
Christians were penalised at a ruck, but Glenstal captain Kevin O’Keeffe instead dropped a goal from 30 metres.
Christians had a chance to equalise three minutes later only for out-half Tomás Quinlan to send his penalty attempt to the right.
The Cork side lived dangerously. Centre Connors was stopped just a couple of metres short of target, but Glenstal got their reward for industry when O’Keeffe was afforded a penalty chance on 28 minutes and he duly converted for a 6-0 lead.
With the last act of the first half, number eight Boland charged over at the posts despite a last gasp tackle. O’Keeffe converted for a 13-point advantage.
Christians hit back and Bradfield was sent in for their first just five minutes after the break and Mintern’s industry was rewarded with the second after 21 minutes.
This was to be Glenstal’s day however, and O’Keeffe, Connors, George O’Hara and particularly Boland were playing key roles.
They finished with a flourish and O’Keeffe sealed victory when he kicked the second of two penalties.
C Healy, M Boland, K. O’Keeffe (capt), H Connors, M Hogan, O Bradley, R Hogan, A Plettenberg, J Healy, J Murphy, B Clancy, N Mulvihill, K Glynn, J Boland, G O’Hara.
J O’Flynn, D Lee, O McSweeney, S McAuliffe, J Bradfield, T Quinlan, N O’Leary, R Quirke, L O’Connor, J Roberts, D Lynch, J Moloney, K. Creedon (capt), E Mintern, PJ Green
Replacements: G Roche for Roberts (40), D Dempsey for Creedon (57).
Referee: S Kierans (MAR).