Replacements used: Conor Hogan for Lennon (25 mins), Arthur Lyons for Rob Sweeney (54), Stephen Bradshaw for Sexton (59-78 mins, temp), Dylan Fawsitt for Richie Sweeney (68), Richie Sweeney for Keller (71), Mark Fallon for Austen (76), Rob Sweeney for McMahon (78).
Replacements used: Dave O'Brien for Lawler (65-69 mins, temp sub), James Ratchford for Carney (69), Niall O'Driscoll for A Ryan (71).
Indeed, good persistence paid off for them with just four minutes on the clock when out-half Johnny Holland comfortably slotted a 25-metre penalty after St. Mary's were penalised for not releasing during a particularly threatening passage of play.
The Templeogue outfit struggled to get a stranglehold in the early stages, but they responded well to the concession of this score.
Reliable full-back Gavin Dunne was on hand to gain parity for his side when he converted superbly from a penalty close to the left touchline.
Following this effort, the game started to even out to a certain degree, but further indiscipline by the St. Mary's defence on 15 minutes gave Holland the chance to reclaim the lead for Constitution, and he made no mistake with his close range kick.
As the action moved beyond the opening quarter, Cork Con started to become more forceful in their play, and a smart move from a scrum six minutes later - instigated by scrum half and captain Gerry Hurley - eventually found its way to Cronan Healy, who produced an inch perfect pass for right winger Robert Clune to touch down in the right corner.
Holland's conversion attempt was wide of the mark on this occasion, but Constitution nevertheless were starting to settle into their stride.
St. Mary's were never going to be dismissed lightly though, and Dunne reduced the gap after 25 minutes with a successful place-kick from a tight angle.
Holland stepped forward to successfully negotiate another routine three-point attempt, but Dunne quickly replied with his third penalty of the contest. With just five points separating the teams, the game was always likely to be finely balanced.
However, Cork Con's hopes of regaining the silverware on offer - they were All-Ireland Cup champions in 2006 and 2010 - were greatly increased two minutes before the interval. Outside centre Scott Deasy drove over the whitewash for a converted try after the excellent Holland has produced a neat offload.
St. Mary's applied some pressure in the closing moments of the opening period, but the compact Con rearguard held firm to take a 21-9 cushion into the second half.
At this point, it looked like the Temple Hill side were in control of their own destiny, but their opponents emerged from the dressing room with renewed vigour.
As the hosts' pack started to exert plenty of influence, they began to make considerable inroads into the Constitution 22.
A relentless period of pressure eight minutes after the restart enabled them to break through for their only try of the day, as bustling flanker Gareth Austen powered over at the end of a strong maul on the right flank.
Dunne's bonus effort from the wing was once again on the money, as Hugh Hogan's charges began to force their way back into the reckoning.
Matters became even more interesting with 25 minutes remaining. Dunne split the uprights magnificently from a distance of 40 metres to leave just two points between the teams during a crucial juncture in the decider.
Last year's Ulster Bank League champions had dominated the play up to this point in the half, and they continued to take the game to the Leesiders, who had struggled to maintain the momentum they had developed before the break.
Cork Con's defence was performing admirably in the face of adversity, however, and they were dealing effectively with much of what St. Mary's were throwing at them.
As the tie moved into the final ten minutes of play, Constitution eased any tension they might have been experiencing with the aid of some smart tactical kicks into opposition territory.
St. Mary's continued to press for the scores they needed to force the outcome in their direction, but their fate was finally sealed as a result of Holland's outstanding drop goal kick from distance three minutes into time added on.
Referee: David Wilkinson (IRFU)