It was spectacular stuff and if Bohemians or even St Patrick's themselves do manage to dislodge Dermot Keely's side from the top of the National league table between now and the end of April then this remarkable night at Richmond Park will doubtless be remembered as a key chapter in the championship story.
As they did in their vital win at Dalymount during December, Shelbourne carved out a very early lead for themselves, Dessie Baker this time capitalising on a fine ball from Jim Crawford and some ponderous defending to fire his team in front after just three minutes.
But, this time, it turned out to be not even close to enough against a St Patrick's side that gradually got the better of the cross-city rivals.
After Richie Foran had given them that lead against Bohemians, Shelbourne had succeeded in making life terribly difficult for their opponents for the rest of the match and they quickly set about attempting to repeat the trick last night. The game became high-paced and fiercely competitive.
Amazingly, Avery John was the only player to be booked in the first period, but several players from both sides were lucky to escape cautions as John McDermott took a characteristically laissez faire approach.
For all the poundings handed out, though, both sides managed to exploit cracks in their opponents' defences.
Of the hosts, Ger McCarthy was comfortably the most threatening of a three-man attack, but it was to be the second half before they were to give Steve Williams anything to save, although, as it was to turn out, the first three times they managed it he was unable to provide the required stop.
He could hardly be made to shoulder much blame for the first, a Liam Kelly penalty four minutes into the second period that followed a needless gift to the home side by John, who apparently found the pressure of having McCarthy breathing down his neck too hot not to handle.
Pat Scully's failure to reappear for the second half was a huge blow for the champions as two nightmarish goals followed. Both from set pieces out on the left and in both cases, floated balls to the edge of the six-yard box were met by entirely unchallenged St Patrick's players.
And, in both - the first scored by Darragh Maguire from a Martin Russell free kick, the second by Robbie Griffin from a Robbie McGuinness corner - Williams had little to do other than pick the ball out of the net.
Given the pace of the game and the fact that there was still just short of a half an hour remaining when it went to 3-1, the prospect of Shelbourne steadying themselves and extracting something from the game was real.
But that hope ended painfully for the visiting supporters five minutes later when Kelly, who had earlier been taunted as a "reject" cut down the left side of the box and had his low driven shot turned past Williams by the outstretched foot of Tony McCarthy.
The latest setback made any reorganisation more or less meaningless. Indeed, far from fighting their way back into things, the title-holders were fortunate that McCarthy didn't make it five with 18 minutes remaining when he was put clean through by a long Stephen McGuinness ball that required a quick reaction from the Shelbourne keeper.
He provided it, but took his second knock of the night in the process and not long after he made way for John O'Hara who might have hoped for better circumstances to get his chance to impress.
Still, he managed it, making a fine stop to prevent Kelly completing his hat-trick with a looping header in the closing minutes of ordinary time. If you really could call it ordinary, that is.
ST PATRICK'S ATHLETIC: Kelly; Burke (Doyle, 41 mins), S McGuinness, Maguire, Croly; R McGuinness, Griffin, Russell (Osam, 79 mins); McCarthy, Kelly (Hughes, 92 mins), Holt.
SHELBOURNE: Williams (O'Hara, 79 mins); Heary, Scully (Hutchison, half-time), McCarthy, John; R Baker, Crawford, Doolin (Byrne, 66 mins), Fenlon, Keddy; D Baker.
Referee: J McDermott (Dublin).
