Written especially for the screen by prolific, popular British novelist Patrick Gale and premiering here Sunday as part of the PBS anthology series “Masterpiece,” “Man in an Orange Shirt” is a moving drama about two love affairs — one just after the Second World War, one in more or less contemporary London — linked by the same third party.

That most of the central characters are gay makes it just a little radical in this context — PBS has appended a disclaimer that “the following drama contains scenes which may not be suitable for all audiences,” which is to say for people who have trouble with same-sex intimacy. (It is not graphic by the standards of contemporary American television.) But even with such relationships no longer uncommon on TV, “Man in an Orange Shirt” still feels refreshingly provocative in its insistence on the ordinariness of gay life.

Apart from Gale telling his story in sections spaced several decades apart, it’s oddly conventional. With its soaring score and meaningful close-ups filled with meaningful looks, it’s the kind of story that Hollywood (and its British equivalent) filmed many times over with male and female characters.

Gale certainly has things to say about the challenges and changes of gay life over the last 60 or 70 years, but this is in no respect an issue drama. His point that people are happier when they aren’t forced, or feel like they have to force themselves, into hiding who they are — and that the wider world benefits from it as well — is a universal one.

Indeed, as one character writes to another hopefully of their relationship, “I want it to go on so long that it feels normal … making toast, raking leaves, sitting in silence.” It’s a passage so nice it’s used twice.

Julian Morris plays Adam Berryman and Vanessa Redgrave his grandmother Flora in the modern section of Patrick Gale's decades-spanning "Man in an Orange Suit," a presentation of the PBS series "Masterpiece." Nick Briggs/Kudos for BBC and Masterpiece

All the performances are fine and full of feeling...but Redgrave is breathtaking...she can fit a lifetime into a line.

The drama begins in modern times, as senior citizen Flora Berryman (Vanessa Redgrave) and her adult grandson Adam (Julian Morris) play gin rummy.

“I didn’t know you owned a cottage,” says Adam, a veterinarian, who lives in Flora’s basement. “Why did you two never live there?”

“I visited once,” says Flora, “but never cared for it.”

Just why becomes clear as the story drops back into the middle of the 20th century, where in dark and hectic battle, Adam’s grandfather, Capt. Michael Berryman (Oliver- Jackson Cohen), encounters and aids a wounded Capt. Thomas March (James McArdle), an artist he coincidentally knew a little at school.

Soon they are in love, and not too terribly later they share an idyll, away from disapproving society, at Michael’s simple country cottage, doing everything that young people in love do before the strictures of postwar British life — where being gay could land you in prison, we are usefully reminded — and the fact that Michael is already engaged to Flora Talbot (Joanna Vanderham) come crashing to meet them.

The second hour takes up the contemporary story, with grandson Adam, also gay and conflicted and unable to form a relationship more satisfying than anonymous meetings engineered through hook-up apps. He’s out to some friends, but not to his grandmother, and knows nothing of his grandfather’s story. Gale takes charge of the old bad line about whom God didn’t create, and puts Adam together with Steve (David Gyasi), who has brought his cat to the clinic. Steve, who will have some professional ideas about the above-mentioned cottage, works and lives with an architect played by Julian Sands.

Joanna Vanderham as Flora Talbot and Laura Carmichael as her sister Daphne in the PBS "Masterpiece" presentation "Man in an Orange Shirt." Nick Briggs/Kudos for BBC and Masterpiece

While Adam and Steve’s story represents the possible fulfillment of a life that seems completely impossible for Michael and Thomas, it’s Flora coming to terms with her own life, with what she has lost and stands to lose, that forms its single, unbroken spine. Vanderham is affecting as the younger Flora — all the performances are fine and full of feeling — but Redgrave is breathtaking, whether she’s keeping her feelings in or letting them out (in a way that suggests she rarely has); she can fit a lifetime into a line, and even combing her hair in a long shot seems more exceptionally present.

Occasionally, Gale will go obviously to a point, as when Michael and Flora marry and we hear the traditional call for anyone who knows why this man and woman should not wed to speak now or forever hold their peace; or when Flora’s young students giggle over the love between Achilles and his pal Patroclus (“But they’re not just friends, are they?”); or when a soldier jovially strips off his clothes to be drawn by Thomas, which, the viewer understands, he might not have done if he’d known that Thomas was gay.

Oliver Jackson-Cohen as Michael Berryman and James McArdle as Thomas March are veterans in love in the wake of World War II in Patrick Gale's "Man in an Orange Shirt," a presentation of the PBS series "Masterpiece." Nick Briggs / Kudos for BBC

And here and there the plotting — especially toward the end of the second hour, which more than once seems to have reached a conclusion — feels imposed by authorial desire for heightened drama rather than arising naturally from the characters and their circumstances. (Chaos ex machina?)

Those are quibbles. For most of its two hours, “Man in an Orange Shirt,” directed by Michael Samuels, neatly knits the cinematic and sweeping with the subtle and specific into a kind of naturalistic melodrama. It will fill you with feelings, if you let it.

‘Man in an Orange Shirt’

Where: KOCE

When: 9 p.m. Sunday

Rating: TV-14-LS (may be unsuitable for children under the age of 14 with advisories for coarse language and sexual content)

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robert.lloyd@latimes.com