Dexter’s sociable and effortlessly charming, initially coasting through life and lacking specific ambitions, more inclined to travel the world and have a good time than burning with desire to change it. But after they get together, they click, enjoying and appreciating their differences until circumstances push them apart.

Yet from the start of the series, I didn’t feel that essential attraction. I didn’t believe that Dex was captivated by Em at college, when she was in her dowdy phase, when he’s supposedly disarmed and drawn to the spirited beauty hidden behind the big glasses and bad haircut.

It was a bit easier to accept later on, after he goes through several life-changing events and she seems to grow into her skin, becoming more self-possessed as she discovers her skills and strengths. But even then, there’s no fateful, fiery spark. This version of Em and Dex seems like characters who might turn out to be mates, trusted companions and confidantes, but never ’til-death-do-us-part lovers.

A couple of key sequences – in a Mexican restaurant and a maze – illustrate the problem. The restaurant scenes, which take place when the characters are in their early 20s, find Em as a frustrated waitress in a cheesy eatery. She’s asked to show new hire Ian (Jonny Weldon) the ropes and she does it with a rapid-fire roast of a tour that indicates her mastery of the job, her lack of illusions about it, her keen mind, sharp wit and natural vitality. Or at least it’s supposed to.

It certainly does in the film, where Hathaway brims with brio, bringing a lightness to her nimble navigation of the space and the delivery of the dialogue. It’s fast and funny, and Ian (Rafe Spall) is suitably dazzled.

Loading

In the series, though, Emma just seems sour and sullen, an impression accentuated when Dex – at that stage a TV star – drops by with his chic new girlfriend.

Feeling patronised and pitied, Em angrily accuses him of insensitivity, of lording his success – however brief and insubstantial it might be – over her humiliating failure. She might be right, but the tenor of the interaction is all wrong. Where she should appear smart and quippy, she’s resentful and judgmental.

In the maze scenes, the pair reconnects following years of estrangement after a bitter falling-out, and both of their lives have experienced significant changes. The occasion is the wedding of Em’s BFF, Tilly Killick (Amber Grappy), and, following a tentative reestablishment of contact, they escape the festivities to wander the hedge maze in the venue’s grounds.

A viewer should feel relief at the repair of the relationship, but also more than that: as they wander through that metaphor for life, with its false turns and concealed pathways, the atmosphere should feel electric.

We should be aching for the Big Kiss, that emphatic, euphoric lip lock, even as Dex’s date, Sylvie (Eleanor Tomlinson), waits impatiently for him inside. It should be a reunion in which they acknowledge what’s been lacking in their lives and what they’ve been longing for.

Loading

Instead it’s, well, nice. It feels like the meeting of two old pals, putting aside past grievances and enjoying an overdue catch-up.

Which is a pity because the series is not without its pleasures. Witty, well-observed and warm-hearted, it’s a lively journey through some seminal stages in life as the engaging characters, separately and together, navigate careers, thwarted ambitions, ill-fated affairs, and constructive and destructive choices.

But it does have a fundamental flaw – and it’s one that afflicts neither the book nor the film adaptation.

One Day streams on Netflix.

Find out the next TV, streaming series and movies to add to your must-sees. Get The Watchlist delivered every Thursday.