The rivalry between Celtic and Rangers is one of the most hostile in world football.
So it's no surprise that when two of football's fieriest characters from either side of the Glasgow divide met there were fireworks.
Legendary Rangers goalkeeper Andy Goram had a brief spell with Manchester United toward the end of his career, answering Sir Alex Ferguson's emergency call.
And it was there he encountered club captain and Celtic fan Roy Keane, with the pair barely exchanging a word while 'The Goalie' was at Old Trafford.
Goram recalled: "Shark’s eyes. Dead, devoid of emotion, glaring at me. No handshake. Welcome to Manchester United, Roy Keane-style.
“The man who saw himself as the heartbeat of the Reds was giving me a message.
“He just looked right through me as an embarrassed Steve McClaren, who at the time was Ferguson’s No.2, tried to introduce the new on-loan keeper to his volcanic captain.
"From that second I knew there was no point in me making an effort with Keane.
“Roy had things that he stood by, things that framed his life, beliefs he clung to with a burning intensity. Well, I had mine.
“What he did to me on that first morning at work at the most famous football club in the world didn’t faze me. It didn’t send me scurrying into my shell. I just thought, ‘F*** it. He’s not going to stop me enjoying this’.
“Keane was a Celtic man, I was a Rangers man. He didn’t like me. End of story.
“Fair enough. After all, I’d done enough to make some Celtic fans dislike me in seven years at Ibrox. There was to be no handshake. Ever.
“The truth is we didn’t exchange a civil word in the three months I was at Old Trafford.
"From day one we had arguments on the training pitch and didn’t get on. It was serious stuff. He hated the sight of me.
“However, I was 36 and I’d landed the move of my life in the twilight of my career.
“Was I going to let one man’s sneering disdain for me wreck the experience? Forget it.
“There were clashes between us. One day in training, we were playing a game of eight-a-side and Keane and Luke Chadwick were up front for my team.
"I always prided myself on the accuracy of my kicking, on being able to pick out a player from a distance, and that day I half-volleyed a peach right on to Chadwick’s foot.
“The kid snatched at it and ballooned his volley over the bar. Suddenly, I was the target of a volley of abuse from Keane. ‘Hey you, give me the f*****g ball,’ he screamed.
"I replied, ‘What, do you get the ball just because you’re Roy Keane? F*** off’.
“The atmosphere was icy from that moment on, and on the way off the field Gary Neville collared me. ‘Goalie,’ he said, ‘we don’t talk to Roy like that down here. We just don’t’. It was a telling insight for me. Of course I respected Keane as a player, but I couldn’t have that.
“As far as I was concerned, the way he spoke to some of the players was bang out of order. Many of them at Old Trafford were clearly s**t-scared of him.”
"The atmosphere was icy from that moment on, and on the way off the field Gary Neville collared me. ‘Goalie,’ he said, ‘we don’t talk to Roy like that down here. We just don’t’. It was a telling insight for me. Of course I respected Keane as a player, but I couldn’t have that.
“As far as I was concerned, the way he spoke to some of the players was bang out of order. Many of them at Old Trafford were clearly s**t-scared of him.”
