According to Wikipedia, Hampstead Heath is a popular public space in London; covering nearly 800 acres, the tract is filled with forests, hills, ponds and meadows — along with a training track, playgrounds and three swimming pools.

Its popular history includes one Harry Hallowes, a.k.a. “Harry the Hermit,” who in the 1980s set up a makeshift shack on the land, where he lived quietly for the next 20 years — until developers tried to evict him for a planned set of luxury apartments.

This obscure story serves as the genesis of “Hampstead,” an amiable, late-in-life love story currently streaming on a variety of platforms. But of course the script makes tons of changes.

For one thing, screenwriter Robert Festinger switches the squatter’s name to Donald Horner; but his chief alteration is to couch the whole thing as a rom-com. This is achieved by adding the fictitious Emily Walter, a cheerful widow who lives near the park and befriends Horner, eventually helping him take his property battle to the courts.

“Hampstead” is predictable and somewhat underwritten, but it floats along in a perfectly entertaining fashion thanks largely to Diane Keaton and Brendan Gleeson in the lead roles.

Since Keaton is much better known than Gleeson, the movie’s trailer leans heavily on her presence here; and indeed, without the actress’s well-known winsome persona, this film would not be nearly so enjoyable. She gives Emily a soulful center that engages us completely, even as we wait for this character to shake off her slavery to upper-middle-class convention and artifice.

But it’s really Gleeson who carries this film; the veteran actor — whose distinguished career goes all the way back to 1989, and who is the father of the similarly busy young actor Domnhall — takes firm control of a role that sways wildly between genial kindness and sharp-tongued misanthropy.

Together, this fine pair keeps “Hampstead” on the rails — the story of seniors so set in their dissimilar ways that the friendship seems almost as likely to crash as it does to help them through their widely different struggles.

The film features a buoyant, upbeat score by Stephen Warbeck and solid direction from Joel Hopkins, who mastered 2008’s similarly themed “Last Chance Harvey”; and the supporting cast is likewise terrific, highlighted by James Norton as Emily’s son and Adeel Akhtar as David’s lawyer.

It’s not going to win any awards, but “Hampstead” makes a charming alternative to this year’s round of depression-inducing Oscar nominees.