Oh, Hampstead, what did you do to deserve Hampstead? Bet you wish the film-makers had pressed on down Fitzjohn’s Avenue and made Swiss Cottage, say. On the other hand, maybe you did have it coming, especially as I once overheard one mother say to another in the Coffee Cup: ‘James? He had so much homework we had to send him to boarding school.’ That always makes me feel better, given I’ll never be able to afford to live there.

This plainly wants to do for Hampstead what Notting Hill did for Notting Hill and Manhattan did for Manhattan and Munich… nope, we’ll stop there. But it’s the sort of ‘love letter’ that should have been scrunched up, thrown in the bin and never mentioned again. Directed by Joel Hopkins (Last Chance Harvey), the film is a romantic comedy — I use the phrase loosely — that took as its starting point the true story of Henry ‘Harry’ Hallowes who, in 2007, was awarded a plot of land on the Heath having lived there in a hut for many years. Here, Harry has become Donald (Brendan Gleeson), and is about to be evicted by property developers (boo-hiss), but finds help and, ultimately, love — not a spoiler; what did you think he’d find? — in the form of an American widow, Emily. (Always ‘Emily’ in these films; never ‘Linda’ or ‘Bertha’ or ‘Sue’.) Emily, played by Diane Keaton with so much kookiness she must have emptied the kook factory, first spies Donald while looking out of her attic window with binoculars. As I’ve always known about ‘the hermit of the Heath’, you do wonder how come you, Ms Emily, live opposite yet haven’t clocked him until now?

Harry, who died last year, blessedly, was, in fact, a cantankerous old sod who told everybody who came near to piss off, but reborn as Donald he strides the Heath like a character from a Thomas Hardy novel, reads poetry at the foot of Karl Marx’s grave in Highgate cemetery and lives in a ‘hut’ that puts your average house to shame. He is also well groomed and sparklingly clean. Yes, he does bathe in the ponds, but if you have bathed in the Heath’s ponds, you will know you come out streaked with mud, stinking of sludge and with duck poo between your toes, if not your teeth.

The film doesn’t offer a single shred of realism. For instance: if Emily is so broke, how come she’s always so exquisitely dressed? As for the script, by Robert Festinger (In the Bedroom), it’s drivel, and also quite misogynistic. You’d better find a man, Emily is told at one point, because ‘if you wait too long you’ll shrivel like an apricot’. Possibly some perfectly nice people still live in Hampstead, although I don’t know for sure, but this has wholly plumped for the stereotypes. True, it makes you feel better about never being able to live there, but it’s lazy all the same. Emily’s neighbour (poor Lesley Manville) is vile, as is the creepy accountant (poor Jason Watkins) who expects Emily to shag him for sorting out her finances. Also, he can’t be a very good accountant, as he never asks about her dry-cleaning bill, which must be astronomical.

Gleeson is a fine actor in most circumstances, but here the material is so thin he’s given nothing to work with, or against, as there are no decent jokes, and there’s almost no drama. Plus, both leads are hampered because there isn’t a squeak of sexual chemistry between them. Indeed, when they first get it together, my instinct was to look away, as I just felt so embarrassed for all concerned. (Also: duck poo in teeth!) So that’s Hampstead for you, and you can take it or leave it. Leave it… that’s probably best.