What daft Manx nonsense is this?

“Mindhorn” is a loopy British farce about a has-been TV star, his former co-star and girlfriend, his former stuntman and a real-life murder suspect so delusional he insists the actor play that part in his little cat-and-mouse game with the local Isle of Man police.

Julian Barratt has the title role, inhttps://twitter.com/The_Mal_Galleryor that of actor Richard Thorncroft, a few decades and many pounds — the fat kind — removed from his signature role, that of a former secret agent experimented on by the Russians so that his super-powered eye (covered in an eyepatch) can discern “the truth” of any situation.

“It’s TRUTH time!”

Back in the day, “Mindhorn” had the cool porn mustache, the cool “capoeira” martial arts skill, cool tan leather jacket, the boots and the uncoolest Jaguar ever — the bargelike ’70s vintage XJS.

He had a sexy sidekick (Essie Davis) whom the actor playing Mindhorn was carrying on with off camera, a dopey but brave stuntman (Simon Farnaby) and another co-star (Steve Coogan), whose character, Windjammer, has gone on to decades of much-resented success in a spin-off show.

Thorncroft took his shot at Hollywood, and the fact that he’s got a ratty wig, a pint-gut and a dumpy flat in Walthamstow — a less fashionable corner of London — tells you Hollywood didn’t buy in. Thorncroft is reduced to begging his agent for news on his “autobiography,” which no one wants, and crashing auditions for a film directed by his old mate Kenneth Branagh.

Not sure he’s the best choice to play a Jamaican mobster, mon.

“Three years at RADA’ll give a man SOME skills!”

Fate intervenes in Richard’s plunge to the bottom. A madman (Paul Tovey) on the Isle of Man, where “Mindhorn” was filmed, is wanted for murder and hiding out in the island’s old smuggler’s tunnels (a real thing). And the only copper he’ll talk to is “Mindhorn.”

Not the actor, but the guy in full kit, full’stache and ugly-ass jacket and Jaguar. The nut calls himself “Kestrel,” and he won’t show himself until his idol is on the case. With his agent smelling “publicity” and Richard sensing his chance to be “back on the map,” it’s off to the isle to mix with the Manxes, as the locals are called.

Maybe he can catch up with that old flame/co-star, now a reporter for MANX TV. Maybe the locals have forgotten the Trumpish label he gave the place, way back when. Maybe not.

He’ll mix with the cops, including Det. Sgt. Baines (She Who Must Be Worshipped, Andrea Riseborough), don the wig and jacket and bully-boy our nutjob suspect into surrendering.

“Comeback,” here we come.

What former “Mighty Boosh” co-stars Barratt and Farnaby (co-writers) were shooting for in this goof of a film — which never played in the U.S –was a sort of Steve Coogan/Alan Partridge styled with-fame/without celebrity death spiral.

As reliably funny as these two are, they not only landed Riseborough and “Chariots of Fire” alumnus Nicholas Farrell and Coogan as co-stars. The Oscar-winning Branagh shows up, and Simon Callow also appears as himself, another client of Richard’s agent, who is played by another big name in Brit stage and screen circles, three time Emmy nominee Harriet Walter of “The Last Duel,” “Sense and Sensibility” and TV’s “Succession” and “Ted Lasso.”

“I believe we’re making another transition, Richard, from unemployed actor to unemployable actor.”

Barratt is all bluster and bloat and letting it all hang out, and he’s a damned stitch in this part. Farnaby, Richard McCabe (as Thorncroft’s hard-times ex-publicist) and dopey Tovey as the dopey Kestrel all score.

The story unfolds in some screwy and unconventional ways. The complications are often amusing, sometimes hilarious and always messy and personal and on Richard’s part, delusional. And the island he once calls a “s—hole” is shown off — on screen — to glorious effect.

What they managed here is no mean feat, the second funniest comedy ever filmed on the Isle of Man. And there’s no dishonor at all in finishing behind “Waking Ned Devine,” is there?

Rating: TV-MA, violence, sexual situations, innuendo, profanity

Cast: Julian Barratt, Essie Davis, Andrea Riseborough, Simon Farnaby, Richard McCabe, Paul Tovey, Nicholas Farrell, Simon Callow, Steve Coogan and Kenneth Branagh

Credits: Directed by Sean Foley, scripted Julian Barratt and Simon Farnaby. A now on Netflix.

Running time: 1:29