Alex Ferguson was joined by coaching staff at Manchester United's training base, The Cliff, as normal at 9am on Friday May 28, 1999.

It was like any other pre-season planning meeting, as the men looked ahead to the 1999-2000 campaign over bacon sandwiches and cups of tea.

But, really, it wasn't like any of the planning sessions to have come before for Ferguson and his staff.

Less than 24 hours earlier they had all been on an open-top bus parade around Manchester, showing off an unprecedented treble of the Premier League, FA Cup and Champions League to an estimated 700,000 supporters.

The crowning achievement of that treble came the night before the parade, on May 26, 1999 in Barcelona – it was Ferguson's masterpiece, the iconic victory of his association with United.

Today's #GoalOfTheDay needs no introduction... enjoy! #MUFC pic.twitter.com/uQB5Of6SmZ
— Manchester United (@ManUtd) May 26, 2020

The Road to Barcelona

United's route to the 1999 Champions League final was by no means straightforward – they were grouped with eventual runners-up Bayern Munich, Barcelona and Brondby, with the Catalans ultimately the one of the three giants to fall before the knockout phase.

A 3-1 aggregate win over Inter followed in the quarter-finals, helped massively by Dwight Yorke's brace in the 2-0 home-leg triumph, before a chaotic showdown with Juventus in the semis.

Ryan Giggs salvaged United a 1-1 draw with an emphatic late strike at Old Trafford in their first meeting, but United appeared to be crashing out in comprehensive fashion when Filippo Inzaghi netted a brace inside the first 11 minutes in Turin – his second taking a wicked deflection off Jaap Stam and looping over Peter Schmeichel.

But a satisfying glancing header from Roy Keane put United back in it, before Yorke's diving header levelled it on the night and gave them the away-goals advantage.

Andy Cole rounded things off late on, tucking in from an acute angle after Yorke had been felled by Angelo Peruzzi. United were in the final for the first time in 31 years.

11 mins: Juventus 2 #MUFC 0
84 mins: Juventus 2 #MUFC 3

An incredible night in Turin - on this day in 1999! pic.twitter.com/6djKzeT4MJ
— Manchester United (@ManUtd) April 21, 2017

'That night in Barcelona'

Ferguson stood on the Camp Nou touchline in the build-up to kick-off. He turned back towards the crowd and just stared as a mass of photographers swarmed in front of him.

He was a picture of calm, pure zen, as he gazed into the seemingly endless maw of seats in Barcelona's gigantic stadium. What was going through his mind? Who knows, but the idea of what would unravel before his eyes was surely not in his wildest dreams.

"My lack of vanity precludes me from being gutted about it," Ferguson had said in his pre-match news conference, as he was reminded of the fact rivals and detractors used his previous lack of Champions League success as a stick to beat him with. "I think what I've achieved stands for itself, and I'm lucky to be able to do that. What I've won as a manager – I'm blessed, so why should I look upon failure to win a European Cup as a tragedy for me?"

Anyone suggesting United were already at a disadvantage at kick-off might've had a point, as they were without the suspended Keane and Paul Scholes, and within six minutes Mario Basler's free-kick found its way into the bottom-right corner.

The many chances continued to come and go for a dominant Bayern, who had Samuel Kuffour marshalling Cole expertly. United were fortunate to be only 1-0 down at the break.

"[Ferguson] then said to us, 'This is the European Cup final - some of you may never get here again - make sure when you come in at full-time knowing that you have given your all and left nothing on the pitch'," Cole recalled of his manager's half-time team talk years later.

The Bayern onslaught continued. Mehmet Scholl's delicate chip hit the post and fell into Schmeichel's arms, before a Carsten Jancker overhead kick came back off the crossbar.

"When the chip hit the post, I didn't turn around at first because I knew that was 2-0 – when I saw it hit the post and come straight back to me, I knew we'd win," Schmeichel told UEFA in 2018.

And United duly rallied.

That night in Barcelona 21 years ago #mufc #throwback pic.twitter.com/q3h4Zs1YxS
— Peter Schmeichel (@Pschmeichel1) May 26, 2020

'Football. Bloody hell.'

Teddy Sheringham had been introduced from the bench for Jesper Blomqvist, leaving United with a single central midfielder – Nicky Butt – as David Beckham moved back towards the right and Giggs to the left.

Lothar Matthaus' withdrawal 10 minutes from time, he felt, emboldened United. Soon after, Ole Gunnar Solskjaer replaced Cole, leaving Ferguson's men with three up top – they were not about to give up without a final push.

"On the bench, we all thought we'd won. There was nothing to suggest United would score. What followed was unbelievable – it was like watching a horror film," Matthaus reflected.

As United enjoyed a late flurry, a Denis Irwin cross in the 90th minute was deflected behind. The corner could only be cleared as far as Giggs on the edge of the box, and his scuffed shot was turned in by Sheringham in similarly scruffy fashion, sparking scenes of disbelief on both benches – Oliver Kahn's half-hearted offside appeal falling on deaf ears.

Manchester United made history #OTD in 1999 #UCL pic.twitter.com/rigKUScuVo
— UEFA Champions League (@ChampionsLeague) May 26, 2020

Another attack up the left, this time led by Solskjaer, brought a second corner in the third minute of stoppage time.

Another tantalising Beckham delivery was this time met cleanly by a United head, Sheringham glancing it on, and before anyone could work out whether it was heading wide or not, the now iconic sentence was uttered on British commentary: "And Solskjaer has won it!"

With Kuffour getting drawn towards the centre of the box, Solskjaer was left in space and he stuck out his right foot to divert Sheringham's flick-on into the roof of the net.

Even in a match as unpredictable as this, United knew there was no way back for the German champions after two goals in 103 seconds. "All the Bayern players were on the floor - they didn't even want to kick off again. We knew we'd won it," Ferguson's assistant at the time, Steve McLaren, once said to the Daily Mail.

Bayern players, officials and sympathisers weren't shy in their lambasting of United and their luck afterwards – though Ferguson's succinct appraisal of the situation summed it up a little better in a post-match interview with ITV: "Football, bloody hell."

Ferguson's career with United was a truly remarkable success – the longevity, the trophies, the 'Fergie time'.

They all sum up this incredible era for United, and that night in Barcelona will be remembered as Ferguson's magnum opus.

But the defining moment? That came 36 hours later, as Ferguson's unrivalled work ethic had him already planning his next successes when anyone else would have surely been nursing the mother of all hangovers.

"But they never give in – and that’s what won it.” - Sir Alex Ferguson.

Today marks the anniversary of that magical night in 1999 – Ole's injury-time goal won us the #UCL to complete the Treble.

History was made. pic.twitter.com/nMlXqtDJyw
— Manchester United (@ManUtd) May 26, 2020