The summer of '99 and almost certainly the best days of Alex Ferguson's life as Manchester United celebrated their historic Treble.
Meanwhile at Highbury, a bruised Arsene Wenger and Arsenal figure out how to rebuild having come so close to denying United in the Premier League and FA Cup.
They look to Italy where a young French winger called Thierry Henry is struggling to adapt to life at Juventus. Henry, then 21, has contributed only three goals in 16 matches. It's not working out.
Wenger decides to fling Henry a lifebelt, paying £11million to end his Juventus misery and duly converting him into one of the most prolific of all Premier League strikers. The rest is history.
It was this moment that Ferguson last week pinpointed as the one that turned his and United's rivalry with Wenger and Arsenal 'toxic'.
'The big change that made Arsenal was reinventing Henry. And the goals… he was fantastic,' Ferguson told a new documentary on Wenger titled: 'Arsene Wenger: Invincible.'
'You're always looking in the rear-view mirror to see who's coming up behind you, and when you see someone you accelerate.
'Arsenal were catching us up, and their team was good enough to go above us, there's no question about that.'
That they did - eventually. United would still win the next two Premier League titles before Wenger's side won their second Double in 2001-02.
Two seasons later came the 'Invincibles' team that even Ferguson has come to admit in the same documentary achieved something more impressive than all his title-winning sides.
He's changed his tune from the time, when through gritted teeth, Fergie claimed the 'Invincibles' drew too many games.
Manchester United versus Arsenal was the fixture and the bitter rivalry that made the Premier League the global phenomenon it is today.
For a good few years, it was pure box office. Not only would the result often have a huge impact on the outcome of the title race but could guarantee drama, sublime goals and a punch-up.
'He was my biggest rival for 10 years. Competition is real - it's you or me,' Wenger said of his rivalry with Ferguson on The Graham Norton Show last year.
'Pain hurts and the biggest pain is to lose a football game. I was physically sick when I lost.'
'He's come from Japan… what does he know?'
Wenger arrived at Arsenal in October 1996 and was a complete unknown in English football.
However, it didn't take too long for signs to emerge that his Arsenal team were capable of challenging United's dominance.
The game at Highbury that season was marred by a clash between Arsenal striker Ian Wright and United goalkeeper Peter Schmeichel.
Wright went for the ball studs-first and caught Schmeichel. They clashed again at the final whistle and had to be separated by police. Wright accused Schmeichel of racist abuse, but the Dane was never charged following a Football Association investigation.
Wenger and Ferguson, meanwhile, traded barbs over the incident. They also clashed that season over fixture scheduling - a rule change permitted an extension to the league calendar, something Wenger perceived as beneficial to United as they chased the title.
'It's wrong the programme is extended so Manchester United can rest and win everything,' said Wenger.
Ferguson retorted: 'Maybe he should concentrate on Ian Wright's tackles rather than Manchester United. He's at a big club, well Arsenal used to be a big club, and maybe next year he could be in the same situation. I wonder what his story will be then.
'He has no experience of English football. He has come from Japan and now he is telling us how to organise our football.
'Unless you have been in the situation and had the experience, then he should keep his mouth shut - firmly shut.'
Fergie also took a pop at Wenger's linguistic skills: 'They say he's an intelligent man, right? Speaks five languages! I've got a 15-year-old boy from the Ivory Coast who speaks five languages!'
Pinot? 'Nah'
Another thing that irked Ferguson during the early years of their rivalry was that Wenger didn't partake in the tradition of sharing a glass of wine with the opposition manager after a match.
Describing the Frenchman as 'aloof', Ferguson complained: 'He never comes for a drink after matches. He is the only manager in the Premiership not to do so. It would be good for him to accept the tradition.'
It wasn't until 2009 that Wenger explained why he turned down the invitation. 'What can you say if you have won? And if you have lost all you want to do is get home and prepare for the next game.'
Haunted by the ghost of Giggs
Arsenal well and truly gave United a bloody nose when they won both the Premier League and the FA Cup in 1998.
United had been challenged by Blackburn Rovers in the Premier League's early years, then by Newcastle's 'Entertainers' under Kevin Keegan, but they'd both faded away.
Arsenal, however, lost out to United in all competitions a year later. In an epic FA Cup semi-final replay at Villa Park, they lost to 10 men thanks to a brilliant individual goal by Ryan Giggs.
Arsenal should certainly have won the game. Roy Keane was sent off and Dennis Bergkamp had seen a last-minute penalty saved by Peter Schmeichel before Giggs slalomed past Lee Dixon and Martin Keown after intercepting a stray Patrick Vieira pass, to blast past David Seaman.
United won everything and Arsenal ended up empty-handed and Wenger believed that was the crucial moment.
'Giggs' goal was what decided their season. I think that goal won them the Treble because if Bergkamp scores I think the game was over,' he reflected in 2015.
'It was a trauma for us. I can still hear the shouts of their team having won, they couldn't believe it because they were down to 10 men.
'And I think that put them on a wave of euphoria and then they won the title - just.'
Prettiest wife contest
United won three consecutive league titles between 1999 and 2001 - even thrashing Arsenal 6-1 at Old Trafford en route to the third of those.
But the Gunners recovered their strength and would win another Double in 2001-02. Ferguson had announced his intention to retire early in the season but performed a U-turn when it transpired he wasn't going to bow out on the intended high point.
Sensing that Patrick Vieira was unhappy at Arsenal, Ferguson reportedly sanctioned a transfer bid for the French midfielder around that time.
Vieira and Roy Keane had already had their share of bust-ups, with Vieira raising his hands to Keane in an August 1999 meeting, but the prospect of them playing together in midfield was mind-blowing.
Wenger accused Ferguson of 'not really respecting the rules' in approaching Vieira, further stoking the rivalry.
Arsenal went on to clinch their league title at Old Trafford in the penultimate game of the season, Wenger declaring a 'shift in power.'
Yet Ferguson suggested his team had played the better football that season. Wenger replied: 'Everyone thinks they have the prettiest wife at home.' It would go down as one of football's great put-downs.
The Battle of Old Trafford
Things really turned ugly between the two rivals at the beginning of the 2003-04 campaign - Arsenal's 'Invincible' season - when they came away with a hugely controversial 0-0 draw at Old Trafford.
Arsenal had started the season without defeat but it so nearly ended when Ruud van Nistelrooy smacked a stoppage-time penalty against the crossbar.
That sparked a pretty wild reaction from Arsenal's players aggrieved by Van Nistelrooy's role in getting Vieira a second yellow card 10 minutes earlier.
Vieira flicked out a boot at the Dutch striker from his position on the ground and Van Nistelrooy's reaction ensured he was shown a second yellow by referee Steve Bennett.
Wenger didn't hold back afterwards: 'You cannot tell me that Vieira is the devil and Van Nistelrooy is an angel. Van Nistelrooy looks a nice boy but on the pitch he doesn't always behave fairly. We saw Van Nistelrooy went for him. I think it is cheating.'
Vieira said afterwards that Van Nistelrooy 'tried to stamp on me and then made more of the challenge than he should have done. He cheated.'
Ferguson kept silent after the game despite the scenes of gloating Arsenal players pushing and shoving Van Nistelrooy after his missed penalty.
Little did we know at the time that Arsenal would still be unbeaten the next time they came to Old Trafford…
The Battle of the Buffet
Arsenal were 49 games undefeated by the time they returned to play United in October 2004.
Ferguson started the pre-match war of words by claiming Arsenal 'got away with murder' after the FA banned Lauren for four games, Keown for three and Vieira and Ray Parlour for one each for the 2003 fracas.
'What Arsenal players did that day was the worst thing I've seen in this sport. No wonder they were so delighted at the verdicts.'
Blue touchpaper well and truly lit, the game was littered with bad tackles, not least Van Nistelrooy going studs-up on Ashley Cole, for which he wasn't punished.
After Van Nistelrooy converted a penalty to atone for 12 months previous and Wayne Rooney sealed a 2-0 win that ended Arsenal's historic unbeaten run, all hell broke loose in the tunnel.
Wenger confronted Van Nistelrooy for the tackle on Cole, but Ferguson intervened and told his counterpart to leave his players alone.
It was at that point a slice of pizza came flying across the Old Trafford tunnel - allegedly thrown by Cesc Fabregas - and hit Ferguson, who was forced to change clothes to carry out post-match interviews.
Ferguson's recollection of events later that season: 'In the tunnel Wenger was criticising my players, calling them cheat, so I told him to leave them alone and behave himself.
'He ran at me with hands raised, saying "what do you want to do about it?"
'To not apologise for the behaviour of the players to another manager is unthinkable. It's a disgrace, but I don't expect Wenger to ever apologise, he's that type of person.'
Wenger responded: 'If he has to talk, he talks. If he wants to make a newspaper article, he makes a newspaper article.
'He doesn't interest me and doesn't matter to me at all. I will never answer to any provocation from him any more.'
This followed a war of words that stretched the toxic fall-out from 'Pizzagate' on for several months.
Wenger had called Van Nistelrooy a 'cheat' in a post-match interview, for which the FA fined him £15,000.
Ferguson described Wenger's Arsenal as 'the worst losers of all time, they don't know how to lose.'
The whole chain of events would be the high point, or low point depending on your opinion, of the United versus Arsenal rivalry.
In his 2013 autobiography, Ferguson said Wenger had come at him 'with fists clenched' and the defeat 'scrambled his brain', their relationship breaking down for almost five years.
Detente
Gradually, the toxicity drained from the Wenger-Ferguson rivalry.
One major factor was Arsenal's decline from regular title challengers with United during the latter part of the 2000s.
In Ferguson's book, he noted how Wenger invited him into the dressing room after the 2009 Champions League semi-final and offered congratulations.
With the emergence of Chelsea and eventually Manchester City as Premier League contenders, the sting was drawn from the feud and relations became more cordial.
Wenger and Ferguson have become friends since their retirements from management. 'We have a lot of respect for each other now. We had a period when it was very tough, very hot,' Wenger said last year.
'After you're not competing any more, everything becomes a bit more objective.'
In 2018, Ferguson had presented Wenger with a gift pitchside at Old Trafford as the Frenchman's 22-year reign as Arsenal boss drew to a close.
The war was, by then, very much over.