The idea, I gather, was inspired by the film Boyhood: to make a factual strand that compressed the passing of years to produce a slice of life that wasn’t sliced too thinly. This Is Our Family (Sky Atlantic) gave film-makers three years to follow their subjects, and develop the kind of relationships necessary to document something personal and in-depth.

The first of four films, made by Clare Richards, focuses on the Borg family of Newport, Wales, specifically Tony and Emma, who are not married but have just got engaged. They seem very happy together, but, before they met, Tony, a boxing coach, was defined by his reputation as a “ladies’ man”, which is one way of saying he has eight children by an unspecified number of mums. Was Emma fully apprised of his past when they met? “Hundred per cent,” she says.

Tony, a gentle but deeply undemonstrative man, is facing up to the fact that some of his children are refusing to attend the wedding, for reasons he can’t, or won’t, fully explain. “The five that aren’t coming are from the same mum,” he says. “It’s quite possible they’ve decided that me getting married to someone other than their mum, perhaps they’re not happy with that.” Maybe a fuller explanation is unnecessary. It seems his children find his newly settled status just as upsetting as his wayward past. “They don’t like this changed man,” says his non-estranged daughter Sherridan.

Emma, who has children of her own, can’t make up her mind about bridesmaids. “I’m either gonna have none or I’ll be having six,” she says, laughing, then blinking back tears. At this point, it becomes clear that the focus of the film isn’t Tony, but Emma, and the subject isn’t marriage at all. It is bereavement.

Eighteen months before the cameras joined the Borgs in 2016, Emma’s 19-year-old daughter, Xana, was killed in a car crash on her way home from a party. Emma had driven past the scene of the accident on her way to work that morning, not knowing that Xana was involved. Her grief is still so raw that Emma doesn’t think she can bear to have bridesmaids without Xana being among them.

Three and a half years later, she still can’t bring herself to commission a headstone for Xana’s grave, or experience any kind of joy without also feeling profound sadness. The driver of the car and another passenger were jailed for their part in Xana’s death, and Emma wonders how she will cope when they are let out (both men have since been released).

In light of all this, Tony’s estrangement from his own children seems more difficult for Emma than it is for him. “They’re his kids,” she says. “And I know what it’s like to lose kids. If I could sacrifice my relationship to have my daughter back, I would.”

Post-wedding comes the revelation that Tony is the father of a ninth child, Shannon, welcomed into the extended family retroactively after a DNA test. When the result comes back, Tony says to her, simply: “Congratulations.” He seems stressed, but pleased, although it is hard to tell with Tony: behind his still expression, his eyes are always darting about warily. “I’m a pretty cold person,” he says. “That’s the way it is.”

From the outset, it is clear that a film this painful, honest and sensitive could not have been made without the time it took to establish an extraordinary level of trust between the film-maker and her subjects. It seems a bit odd that Sky, having taken such pains to lay the groundwork for the series, had no correspondingly generous assessment of its audience’s attention span: shorn of ad breaks, the whole thing is fewer than 50 minutes long. Partly, of course, the compression is the point – the viewer experiences it as a form of time travel. But three years in under an hour is a brisk trot, one that necessarily leads to some blurring.

What you are left with is a closely observed study of two people coping with grief and estrangement with courage, patience and humour. Above all, the film exposes the extraordinarily complex emotional lives of people, who from a distance may seem to be the sort who just get on with things. It reminds you that everyone just gets on with things, and no one does.