The worst-kept non-secret in sport is finally out. As of Monday afternoon José Mourinho will, barring last-ditch turbulence, be appointed Manchester United manager, the consummation of an epic, slow-burn seduction that has hovered behind the headlines for six months.

For United’s players Saturday’s FA Cup final victory against Crystal Palace has turned out to be less a new dawn, more a kind of Viking funeral for the Louis van Gaal era after two seasons of meandering stasis. Even as Van Gaal was marching into a sullen Wembley press conference with the trophy under his arm, pictures were filtering through of Mourinho just across town at the David Haye fight at the O 2 looking coy and sultry and pregnant with mischief.

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Van Gaal is a revered football coach, for all the social media snark and newspaper ribbing he has attracted during his time at this drifting, stalled Manchester United. But this was a humiliating experience: a proud man, sitting with the venerable shiny cup plonked defiantly on the table in front of him while the assembled global media were already peering over his shoulder at the next guy. How very Mourinho – ruthless even in absentia.

The talk now is of a three-year deal for Mourinho at Old Trafford, resolution at last of an extended public courtship curated by a cast of super-agents, deal-makers and willing media accomplices. Indeed there is a feeling of delayed destiny about the whole process, a relationship that has sparked at one remove ever since the first sighting 12 years ago of this thrillingly handsome, absurdly young coach – dubbed by the Sun “a Portuguese man of Pwhoaar” – sprinting along the Old Trafford touchline as his Porto team eliminated United from the Champions League.

And so here we are. Darth Vader has entered the Death Star. The only real question now is why so many people around the club, from fans to directors to associated media, seem to think this is unquestionably a good idea.

It might sound odd for such a successful coach but Mourinho to United is essentially a celebrity appointment. The only sense in which it resembles a perfect fit is as an injection of glitz, a burnishing of the brand. Mourinho does not deliver thrilling attacking football. In swapping him for Van Gaal United have traded gruelling possession play for gruelling defensive counterattack, albeit with a cinematic presence gesticulating on the touchline.

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Mourinho does not behave nicely. He does not bring young players through. He is as far from that more preciously nurtured idea of how United like to see themselves as the vampiric corporate owners, the Glazer family, for whom the club has simply been a wondrous source of income, the ATM that never closes.

It seems obvious that the right move for United, driven purely by the will to build again, would be to hire the best youngish manager in Europe and shower him with support, cash and patience – Unai Emery, for example, a triple Europa League winner with Sevilla, or Thomas Tuchel of Borussia Dortmund, Germany’s fashionably beaky and brainy coming man – someone with a clear plan, no cobwebs, a sense of genuine unspent energy.

Instead a listing giant has hitched itself to another star vehicle in need of an uplift. Mourinho may have won two league titles in the past five years and been sacked by a close rival this season. He may have seemed frazzled in the end times at Chelsea, obsessed with pointless detail, diminished on some fundamental level. But he remains unanswerably A-list – famous, charismatic, endlessly quotable – even if this is to a degree the equivalent of a celebrity marriage of convenience designed to revive a pair of flagging middle-aged careers, a McBusted of a managerial appointment.

And yet such is Mourinho’s drive and United’s depth of resource there is still a strong argument this could all end up working out nicely. At the very least he will surely bring a return to the top four and Champions League football. Above all he really, really wants this. As long ago as 2009 Mourinho was already pouting in United’s direction. In 2012 he thought he had the job once Sir Alex Ferguson was gone, only for United to appoint the desperately paddling David Moyes. Mourinho has simpered and sweated and haggled for this opportunity. And now Heathcliff has finally got his hands on Wuthering Heights. It is unlikely to be dull.

For one thing Mourinho has the will and the self-possession to take a sledgehammer to United’s jerry-built squad, a fudge of odds and ends assembled under three very different managers. He will want to buy a huge amount of players instantly, as he has in the past. At Chelsea more than £70m of post-Soviet fossil fuel wealth was disbursed in his first year.

Money will be spent, but it would take a wilful kind of vandalism not to trust in the progress of supremely talented players such as Anthony Martial or even Marcus Rashford, a lovely, bold, athletic, ball-playing forward who produced United’s best moments at Wembley. Wayne Rooney, a José favourite, will no doubt remain a key peg.

Mainly, though, he will build in the usual style, from the back: two strong centre-halves, full-backs who defend, muscle in midfield. And beyond that a sprinkling of José power, that fine-point attention to detail and the inspiring, inflammatory presence of a manager who believes the game itself starts with his first pre-match press conference.

In this respect it is easy to tire of Mourinho, as many of his players have. But it is also easy to overlook the best of him in that fug of bile and misdirection.

There have been three outstanding periods in his career. Winning the Champions League with Porto in 2004 is a feat to rank close to, if not alongside, Claudio Ranieri winning the Premier League with Leicester. Internazionale’s Champions League win was a triumph of will, spirit and organisation. Driving Chelsea on to league titles in 2005 and 2006, huge pot of spending money notwithstanding, was a fine standalone achievement.

What all these have in common is their tinge of underdog. Mourinho has not quite been Mourinho when success has been expected, as at his three seasons at Real Madrid, when his job has simply been to deliver with a certain elan. He functions best as an outsider, a spoiling force, there to stomp over everybody else’s party.

And from this point of view perhaps this really is the ideal moment for Mourinho finally to land the United job. He goes there with the brief of revival, regearing, reeling others back in. United have finished 7th, 4th and 5th the past three seasons. Upwardly mobile success, tweaking the nose of those who have forged ahead, suddenly looks like a very José kind of brief.

There are those who say even this will be beyond him, that Mourinho has had his decade at the top, the usual life span of the über-manager. There are simply too many battles for him to fight now, a renewal of hostilities with Arsène Wenger overshadowed by the very personal bile of his relationship with Pep Guardiola, who will take over at Manchester City this summer.

All that really seems certain is that in the end Mourinho to United became pretty much unavoidable, the only move left on the board for both parties; that – who knows – United might just have appointed the right man, if perhaps for the wrong reasons; and that above all it promises to be horribly watchable.