Jack Charlton is, almost certainly, the most popular Englishman in the history of Ireland. Thanks to his direct approach, on and off the pitch, the Irish national football team appeared in three successive major tournaments between 1988 and 1994. It’s a run no manager has come close to replicating since.

How Jack managed this feat is at the heart of directing duo Gabriel Clarke and Pete Thomas’s documentary. They detail what Jack needed to do to make the Irish team successful. How he sought any player with an Irish ancestor to increase the size of his talent pool. How he brought a non-nonsense attitude to the dressing room. How he was driven by the love of the Irish people.

And that’s where the film gets even more interesting. Not limited to on-field antics, this is a piece that investigates Jack’s approach to life, and how the people of Ireland took him in. Clarke and Thomas get into all areas of Jack’s life, from his frosty relationship with his brother, the more successful footballer, Bobby (who has, more recently, developed a similar brain disease). And, tragically, how Jack’s life was brought to an end by dementia.

The irony in the film’s title becomes abundantly clear early on – as we, the audience, find Jack Charlton, find what made him tick, what made him popular, and what made him successful, we witness his family lose the man they love. We see, in heartbreaking detail, the shell of what is left as his family watch him slip away.

In a way, Clarke and Thomas are building the memories for Jack Charlton, as the man’s own slip from his grasp.

Few in the TV world would have been more privy to Jack’s time in Ireland than Clarke, the former ITV Sport producer/ presenter, who has more recently turned his hand to documentaries, has struck gold with Jack. For Charlton kept copious notes, scribbled on post it notes and napkins. Those notes form the backbone of Thomas and Clarke’s narrative, giving launch pads for new lines of inquiry as they investigate the man’s career, quizzing the people closest to him.

Those talking heads include the likes of Andy Townsend and Paul McGrath, key players in Jack’s greatest team. The latter, in particular, providing a source of further heartbreak as he talks about his battles with depression and alcohol, telling of how Jack – like a father figure – dealt with McGrath and his demons. It’s a story that, like many offshoots in Finding Jack Charlton, could provide a feature length film in itself.

Given the sheer volume of footage available from the tournaments, it would be easy for Clarke and Thomas to focus on the football. To show us the triumphs in West Germany, Italy and the USA. But while those tournaments do provide the most enthralling chapters (and, oddly for such well-covered events, the directors choose to supplement the footage with dramatic re-enactments), they don’t dwell for too long. They know that the truly powerful moments don’t happen in front of 100,000 people, rather, they happen in intimate surroundings.

But there’s only so much they can get through. The film hints at a bigger picture concerning the dementia that has affected numerous ex-footballers, but there isn’t enough run time to get into the heart of the matter. It’s a film for another time, perhaps.

Here, Clarke and Thomas have crafted a truly touching, sensitive and poignant film that gets to the heart of jack Charlton, a film that deserves to sit alongside the likes of Senna, and Asia Kapadia’s similarly-styled Diego Maradona as a beautifully realised, and brilliantly constructed, character study. They found Jack Charlton, just before we lost him, and for that we can be grateful.