Everyone has heard of 'Pizzagate', right?

Back in 2004, in the tunnel after a Manchester United v Arsenal match at Old Trafford, tempers boiled over between staff of both clubs and a brawl ensued. A slice of pizza was then thrown at Manchester United manager Sir Alex Ferguson, allegedly by Arsenal midfielder Cesc Fabregas.

Well, former Celtic midfielder Alan Thompson almost started a riot over 'Lucozadegate' 12 months previous at the UEFA Cup final in Seville.

Celtic were playing Porto in the showpiece and Martin O'Neill's players were getting wound up by Jose Mourinho's side's antics. Thompson decided to take matters into his own hands as Celtic trailed 1-0 at the interval.

He rarely missed the target during his playing days and this time his aim was straight and true as he threw the drink in Mourinho's face which led to all hell breaking loose in the tunnel.

READ MORE: Cameron Carter-Vickers through the eyes of his former coaches

Speaking about the incident, he said: "There were all sorts of antics from Porto on the night that made lots of people - myself included - unhappy.

"Porto were a good team and it was our job to deal with that in a professional manner.

"It still bites you a little bit when you think about it and I feel for the lads and all the Celtic supporters who forked out their hard-earned cash to go to Seville.

"We still laugh at the barney at half-time with Jose Mourinho and the coaching staff. I squirted some Lucozade in Mourinho's face in the tunnel and all hell broke loose.

"Mourinho was a bit arrogant, shall we say, and when he went to Chelsea, he called himself 'The Special One' and all that.

"We were heading down the tunnel at half-time and the Celtic players were annoyed at their time-wasting.

"I can’t remember who started a scuffle but it was all handbags really.

"I had a full bottle of Lucozade. I think Mourinho was going off on one about something or other and I just stood back and took aim and squirted the drink and it caught him full on the face.

"It caused a bit of a rammy. I didn't finish it as I bolted back to the dressing room. That's the time when you hide behind the likes of Bobo Balde and Rab Douglas."

It's 20 years since Celtic succumbed in the blistering heat of Seville to the Portuguese side and Thompson still feels that had they been able to call upon the services of John Hartson, then they might have got their hands on a coveted winners' medal instead of a runners-up gong.

However, he concedes that despite their time-wasting and dark arts, Porto were still a formidable football outfit.

"It's unbelievable to think that Seville was 20 years ago. That's mad isn't it? Where did the time go?" he continued.

"I still maintain to this day that if John Hartson available to us then he could have come on and made all the difference.

"Sadly John wasn't fit and it was not to be. Even now, 20 years on, people still talk about Seville before any of the title wins and they all have their own special memories.

"Stuttgart, Anfield, Boavista, the Celtic supporters still want to talk to me about those nights.

"We beat some very good teams along the way to reach Seville but it was not to be in the end.

"The Celtic fans talk about where they were when I scored against Liverpool at Anfield in the quarter-final during the run and when we knocked Barcelona out of the UEFA Cup the following season.

"Supporters remember it in infinite detail and it never ceases to amaze me.  I think it is utterly amazing that after two decades, the fans still talk about Seville, yet we lost that final.

"Can you imagine what it would be like if Celtic had won the damn thing?

"What I will say is that for Porto to go on and win the Champions League, the following season shows you how good a team they were and exactly what we were up against."

Thompson has a treasure trove of European memories from his time at Celtic. He scored away to VfB Stuttgart as well as the mighty Bayern Munich in the Olympic Stadium. He is best remembered for his ferocious low free-kick in the 2003 UEFA Cup quarter-final against Liverpool that set Celtic on their way to a 2-0 win over the Reds and a comprehensive 3-0 aggregate victory.

It was ample revenge for the likes of Thompson and Chris Sutton, who had endured miserable times at Newcastle and Chelsea respectively. The win served as the proverbial two-fingered salute to the critics who thought they couldn't still kick it.

That might on Merseyside is also memorable for a team talk given by Martin O'Neill that sent shivers down the spine of every Celtic player. Although Thompson can't remember the chat exactly, he joked that Hartson - who has gone on the record to the Celtic Way to recall it - has been economical with the truth.

He said: "The goal at Anfield was really special to me. It was great for the likes of myself and Chris to go back down to England and prove a point.

"We had not had the best of runs in the Premier League with Chelsea and Newcastle. You kind of get forgotten about and written off and it was nice to go back and show them that you could play.

"It was a sweet moment and we played really well. We didn't nick a 2-0. We were well worth it.

"Martin O'Neill's Anfield team talk was legendary and has entered into Celtic folklore. I am hopeless at remembering stuff like that but all I know is that we walked out onto that pitch feeling ten feet tall.

"I have heard Hartson recounting it in glorious detail but I'm convinced he's at it and just made it all up.

"When people put stuff on Twitter and say its been 20 or more years since Seville happened and they flash up my goal against Liverpool at Anfield or my header against Bayern Munich in the Olympic Stadium or the winner against Barcelona it always makes me smile as you have to enjoy the good memories.

"That's one of the great things about social media every now and then it will remind me of things I did in my career.

"I loved the big games and the build-up to them. It just seemed to bring out the best in me.

READ MORE: Why the safe-standing section should be expanded at Celtic Park

"I know I fed off things like that all throughout my playing career.

"It is also a reminder to myself and the wider general public that I could actually play a bit."

O'Neill's whole Celtic team could play a bit, that's for sure.

If ever an era could have been summed up by a crowning moment, then it would have been Celtic's class of 2003 winning in Seville.

It's the team that gained respect both domestically and abroad. They re-established Celtic as a European force once again.

They went toe-to-toe with the best that European football had to offer and seldom left empty-handed.

Celtic Way:

To his credit, Thompson has gone head-to-head with some of the most illustrious names in the game - Paolo Maldini of AC Milan, Alessandro Del Piero of Juventus and Ronaldinho at Barcelona to name but a few.

"When I signed for Celtic, I knew I would win trophies and medals but I never knew the Seville Celtic team would put the club firmly back on the European football map," he said

"That was Celtic's first European final in 33 years. That's astonishing when you think about it really.

"We had some great European nights in the Nou Camp, San Siro, Olympic Stadium, Anfield as well as Celtic Park so it was all magical.

"I played against the likes of Paolo Maldini for AC Milan, Alessandro Del Piero at Juventus and Ronaldinho at Barcelona, who was probably the best player in the world at the time. And when you look back you can't help but think they were great days.

"Seville was a fantastic memory but it is a crying shame that we couldn't get it over the line.

"My abiding memory of the experience is standing there before kick-off knowing that you are representing a wonderful football club in a major European final was something else.

"I've rarely felt prouder but the dejection and deflation after it was over was so hard to take.

"When we got back to the hotel, we had a dinner organised but that got cancelled.

"I don't even think we sat and had a beer or anything. Everybody just went to their beds as we were so deflated. We just wanted to get the flight back to Glasgow.

"That feeling of dejection stays with you for a while. We put in so much effort to get there and we fell at the final hurdle and getting a runners-up medal is not what you set out to achieve.

"Henrik Larsson came close and everybody thought he was anointed and that he was going to get a hat-trick and Celtic would win the UEFA Cup.

"It didn't happen, unfortunately. There were a few tears shed by a lot of people on the night.

"Paul Lambert had won the Champions League, Chris Sutton had won the English Premier League title with Blackburn Rovers and we had international footballers in the team like Stiliyan Petrov, Johan Mjallby, Neil Lennon, and of course Henrik.

"They had all played at the top level.

READ MORE: Why Celtic's youth loan policy must change going forward

"It would have been nice to mark that era with a European trophy as I think Martin's team deserved to do that.

"It would have been great for Martin for what he achieved at Celtic when you compare what he walked into.

"He was the figurehead and he was at the top of the tree but the dressing room policed itself as we had so many leaders in that team.

"If anyone stepped out of line they got double-barrelled and that didn't come from the manager it came from the players.

"For five years, that team brought their best to the table.

"We didn't turn up on a couple of occasions but predominantly when we were asked the question, we came up with the answers."

Some 20 years on from that fateful night in Seville, Thompson hasn't been able to bring himself to watch the 2003 UEFA Cup final in its entirety.

"I have never watched it back and I don't know if I ever would. I have seen the goals but that's it," he said.

"If I could sum up Seville in one word then it would have to be heartbreaking."

Sadly two decades on from Seville, that gut-wrenching feeling for every Celtic supporter remains the same today as it did back then.

Alan Thompson's book 'A Geordie Bhoy', the story of a Celtic and Bolton hero, is available to buy here.