Much as the internet wills it otherwise, football inhabits the grey areas: everything is subjective, nothing is absolute, and it is no more deviant to change your mind than it is fraudulent to say you don’t know.

However, certain truths are elemental, and here’s one: the 1996-2005 rivalry between Arsenal and Manchester United is the greatest the English game has seen, with – cue Arsène Wenger internal voice – quality, intensity and animosity beyond compare. And, though 2005’s “I’ll see you out there” encounter comes close, its zenith – and therefore English football’s zenith too – was the 1999 FA Cup semi-final replay, which featured every aspect that can possibly eventuate when 22 people gather to boot a pig’s bladder around a green field.

Related: Gary Neville: 1999 FA Cup win over Arsenal was only game I ever smiled in

For that, we have David Elleray to thank. Not words anyone was ever supposed to write. But in the first game he failed to grasp that Ryan Giggs had knocked the ball down the line to himself so, when Roy Keane forced the subsequent cross past David Seaman, he called offside and a drab game ended goalless.

Before the teams reconvened, Alex Ferguson cornered David Beckham and Giggs, urging the former to focus on the simplicity of his ball-striking and the latter to relax into the extravagance of his ball-carrying. Ferguson also replaced Dwight Yorke and Andy Cole with Teddy Sheringham and Ole Gunnar Solskjær – a move that suggested he’d downgraded the game but was actually a masterstroke. “I had got used to Cole and Yorke,” Tony Adams wrote in the Observer. “Now United had a new dimension with two fresh pairs of legs, two players fired up, and they relished it.”

And Sheringham was central to United taking the lead, cleverly shielding the ball for Beckham to absolutely focus an outswinger that spat, shrieked and hissed past Seaman when nothing of the sort seemed remotely possible. It was the first time Arsenal had trailed in 17 games.

United then missed various chances to kill the tie, and were made to pay when Dennis Bergkamp scored a deflected equaliser. Shortly afterwards, Nicolas Anelka put Arsenal ahead; he was thoroughly ensconced in the bosom of the crowd before observing another offside call.

Though Roy Keane was then sent off, United hung on until, with seconds remaining, Phil Neville conceded a penalty. For all of Peter Schmeichel’s brilliance, he had saved just three in his United career, but the iceman Bergkamp, who had missed two of his last five, delivered a weak kick that was easily pushed aside; naturally, Schmeichel celebrated by losing his temper with those who deigned to celebrate their salvation.

So it was that in the second period of extra-time Giggs intercepted a “weary one from [Patrick] Vieira”, swaying past Lee Dixon and Martin Keown before pulling himself between them like a man dashing on to a departing train. He was through! Adams, sliding in, had realised the danger, but Giggs kept his head to absolutely relax an epochal jazzer high into the net before wrapping the entire planet in a balm of luxuriant chest-hair.

At full-time, Gary Newbon suggested to Ferguson that his players hadn’t needed so gruelling a battle. “Look, who’s to know what’s gonnae happen in football, Gary?” Ferguson replied. “It could all blow up in our face at the end of the day, but can you forget moments like this?” A nervous “no” is faintly audible.

“Our supporters will be talking about that for years, the players will be talking about that for years, that’s what football’s about, trying to reach peaks and climaxes to a season, which we are doing at the moment. We’re in a final, we got something in the bank for ourselves, now we go and win this league now.”

Certain truths are elemental.