Diehard Celtic fan Steve Conroy walked out onto the Parkhead pitch and was intoxicated by the astonishing atmosphere – the only issue was he was the referee!
It was the vital new year game in 2010 with Tony Mowbray chasing down Walter Smith, whose side held a seven-point lead.
It was Conroy’s first and only Glasgow derby – and he left his fellow Celtic supporters sick by disallowing a goal and failing to send off Kyle Lafferty.
And he has revealed that he had to kid on he was a Dumbarton supporter - because it's simply not on to reveal your allegiances if you follow one of the big two.
Sadly, Conroy was lost to the game two years later when he felt the SFA didn’t back him properly over a penalty decision in favour of Rangers against Dunfermline.
He told the Get Involved Referee podcast: “My claim to fame is that I was the first non-FIFA ranked official to cover an Old Firm game and I don’t think there has been one since.
“It didn’t work out the way I had hoped in terms of the way I was treated afterwards.
“But there are very few that can say they have refereed a Celtic-Rangers game at Celtic Park.
“I remember being told in the week building up to the game ‘don’t look at the crowd’ – I looked at the crowd.
“I was nervous as hell the couple of nights leading up to it and could hardly sleep.
“Until you experience it you have no idea what it’s like. It’s a cliché, but the hairs on my arms and neck were literally standing on end.
“It was an amazing feeling.
“Even although we were all connected on the communication system, I couldn’t hear a thing.”
Scott McDonald’s goal was cancelled out by Lee McCulloch’s header on a day that was clearly better for Rangers but Conroy was under the spotlight.
He said: “There were a couple of incidents and I’ll admit I got one wrong. I should have sent off Kyle Lafferty but I cautioned him.
“It was a straight leg challenge on Andreas Hinkel and it should have been a straight red.
“I was too far up the pitch and I was at the wrong angle so I didn’t see it properly. It was only when I saw it on video later that I realised.
“If I had been in my normal position and I had a side-on view I would have sent him off.
“The annoyance for me is that there were two other officials who had that side-on view and I didn’t get helped out.
“I also disallowed a Celtic goal when Marc-Antonie Fortune put the ball in the net. I have watched in hundreds of times and I’m still perfectly happy with the decision.
“He didn’t break his arms – but he stopped Rangers goalkeeper Allan McGregor from taking the ball so it’s a foul.
“When I was summoned to the SFA for the debrief I was told by the referee’s supervisor that my decision was “a matter of opinion” and they were going with the opinion of the match observer who had a different opinion.”
It was a day he will never forget for a number of reasons. After retiring in 2012 he subsequently revealed Celtic were his team, but he insists it is taboo when you’re working for obvious reasons.
He said: “Down south if you have an affiliation with a team, you don’t ref them.
“Up here we all get into the game to be a ref in top games and being from the west of Scotland the vast majority either support Rangers or Celtic.
“So if we operated the same system as England, who would be reffing the games?
“You simply can’t declare it – I used to say I was a Dumbarton fan.
“Somehow the SFA know it. You used to get allocated a lot of pre-season friendlies for the team you supported!
“Some Celtic supporters might ask ‘what kind of Celtic fan was Steve Conroy that he disallowed a Celtic goal and failed to send off Kyle Lafferty?’ – he was a very upset one.”
