There were a few fluttering hearts amongst the Fife fans with 20 minutes gone, when Alex Burke put the ball in the Fife net from a clear offside position two yards out, following a game of pen box ping pong.
East Fife had a great chance to open the scoring on 29 minutes when Stevie Nicholas was put through but shot wide, with St Mirren's only reply being a 25 yard effort from Billy Mehmet being easily held by Willie McCulloch.
And that was pretty much that for the first half. St Mirren had the greater possession, but the Fife had the more dangerous efforts and at least had efforts on goal! We were certainly more than holding our own.
The defence of both sides were on top for the start of the second half, with neither team posing any real attacking threat.
Eight minutes in though and East Fife won a corner on the left. Ryan Blackadder swung it in perfectly but the St Mirren defence cleared but only as far as Stewart who looped the ball back into the box and as Jonny Smart went to meet it, he was heavily clattered from behind by St Mirren goalie Chris Smith. The Fife fans wanted a penalty but the ref was having none of it. Having watch the incident again on video, it looks even worse second time around.
Unsurprisingly Smart needed some lengthy treatment and whilst the fans were singing that they all dream of a team of Jonny Smart's, big Smarty was clearly dreaming of spinning stars and yellow canaries.
As the hour mark approached, St Mirren had a penalty appeal turned down, with the player looking to have gone down a wee bit too easy from a good challenge.
And then it happened.
63 minutes gone and Craig O'Reilly, who had come on for Paul Walker at half time, collected a ball forward and ran at the defender before cutting inside and unleashing an unstoppable 20 yard shot over Smith and into the top corner.
The Fife fans were sent into raptures and it was 1-0 to the Third Division Champions elect. Only downside was that the ref saw fit to book O'Reilly for celebrating, presumably because he ran off the pitch and to the dugout area. Hey, I'm sure he won't mind!
You would have thought that this goal would have given the SPL side the kick that they needed but susrpisingly they were happy to knock the ball about in every direction except forward. Frustrating for the Buddies fans but fine as you like for the Fife faithful.
As the last ten minutes came along, St Mirren did try to up the pressure a little but all they could muster was a weak long range header from sub Alan Reid, which McCulloch got down to hold without any real problem.
John Martin had a chance to wrap the tie up when he outpaced two St Mirren defenders, before a last ditch leg from the last Buddie allowed Smith to collect, as Martin went over the St Mirren keeper, but the ref was right to wave away the penalty appeals.
As the full time whistle approached it was disappointing to see St Mirren keeping hold off the ball after Blackadder had put the ball out to allow an injured St Mirren player treatment, but unsurprisingly nothing came of their next attack.
Craig O'Reilly had the last chance of the match in the dying seconds, when he spotted Smith off his line but his effort was held mid air by the St Mirren keeper.
As the final whistle came, the already empty Love Street became even emptier and the Fife fans, players and officials were absolutely jubilant at one of the biggest Fife shocks in living memory and a deserved one at that.
St Mirren were very disappointing. I don't know whether Gus McPherson underestimated us or not but he put out pretty much a full team. They just didn't rise to the occasion.
As for the Fife, all 13 players that were on that field were tremendous. I can't speak highly enough for them and I just hope we get a cracker in the next round.
For me, I don't know whether I would say that game was bigger and better than the Hibs Cup shock in 84 or the Rangers draw in 86. They were both at Bayview, this was away, but I think I might have this just sneaking below the Hibs game.
It's weird really. Tonight's result means so much to me. The Hibs replay was my first ever East Fife game and I've been going ever since. The game tonight was my last East Fife game I'll get to see before emigrating to Canada next month. Don't know when I'll get to see my next one, but lads, that was one hell of a send off. Thank you from the bottom of my heart.
C'mon the Fife!
FINAL SCORE: St Mirren 0 - 1 East Fife
EAST FIFE: McCulloch, McDonald, Fotheringham, Smart, Tweed, Blackadder, Gordon, Stewart, Nicholas (Martin 49), Walker (O'Reilly 46), Cameron. [Subs Not Used: Fox, Linton and Young]
Every single player on that pitch tonight gets three points. No one should be singled out. It was the ultimate team effort.
[Watch Craig O'Reilly's winning goal again HERE]
[For best results though download the goal directly by typing in http://www.aftn.co.uk/oreillystmirren.WMV]