“In this game, there’s what you know, an’ what you DON’T know,” grizzled ex-con and OAP (Old Age Pensioner) Terry fumes in “King of Thieves.” And in a line that can be applied to all those too young to appreciate or “get” this old school heist picture, aka the callow critics who panned it, he ads “And if you don’t even know what you don’t know, you know f— all!“

If the very idea of Oscar winner Jim Broadbent, playing a rare late-career tough guy, chewing through those lines in the presence of still-a-little-scary Oscar-winner Michael Caine, doesn’t thrill or at least tickle you, well this isn’t the film for you.

Maybe you have to be older to appreciate the diabetes/UTI/deaf/napping and insulin-injecting with a slap-on-the-bum afterward charms of “Thieves,” which stars those two, and Oscar-nominee Tom Courtenay, Charlie Cox (“Daredevil”), Paul Whitehouse (British TV and “Death of Stalin” veteran) and hell’s bells DUMBLEDORE himself, Michael Gambon.

But I dare say even those who panned this perfectly engaging, reasonably suspenseful, nostalgic and even whimsical geriatric burglar’s tale when it had its limited theatrical release would agree with me on one salient point.

It’s the very definition of “Netflixable.”

“Thieves” is based on the true story of Britain’s Hatton Garden Safe Deposit heist of 2015.

Caine plays Brian, a bored, comfortably-retired and just-widowed ringleader (of course) who promised his wife (Francesca Annis) he’d “stay out of mischief” just before she died. That changes basically at her funeral.

There’s Terry (Broadbent) and nervous, “stone-deaf” Kenny (Courtenay). And putting on a show by doing a handstand in the middle of the solemn occasion is “the young one,” Danny (Ray Winstone).

The first thing we notice about this informal “mob” is that they’re elderly, inclined to be a bit loud because of hearing issues, and indiscrete. They start chatting up possible “jobs” just to make small talk into shop talk.

A former protege of Brian’s, the on-the-spectrum shy “Basil” (Cox) overhears this, and mentions to Brian that he has a friend who has a key into one of the most-challenging-“jobs” the lads were discussing. Basil may not like to be in crowds or be touched, but he has access to that diamond distrct key, and he just might be “the best ‘sparks’ man (electronics/security systems) in London.”

All they need to do is get in, pry open this or that, use a disused elevator shaft, drift a hole big enough for “the most undernourished thief we can find” — so they recruit Carl (Whitehouse) — to get through and ransack a safe deposit-box filled vault with diamonds, cash and gold, all while avoiding London’s omnipresent CCTV cameras.

Before the Cockney heir to Caine’s perfect Cockney Winstone can say, “‘ello me old son,” that’s just what they do.

For a movie that’s basically a true-to-life “Going in Style,” “King of Thieves” never crosses the line from “cute” to “cutesy.” Caine gives us a taste of his still-hard-as-nails edge, Broadbent and Winstone match him and the picture’s inevitable “no honor among thieves” story arc clings to credibility, first to last.

The casing-the-joint/assembling-the-team/planning the heist scenes are handled with brisk montages set to period pop by Tom Jones or Shirley Bassey, or a crackling jazz score by Benjamin Wallfisch. He sets the actual break-in sequence — it doesn’t go easily or go off like clockwork, BTW — to an energetic jazz version of “Dance of the Sugar Plum Fairies.”

The cute stuff has to do with this guy’s “incontinence,” that one’s need for naps, mid-heist and bonding over “Type 2? Diabetes?”

Gambon shows up as an out-of-his depth fishmonger/fence, Billy the Fish. Gambon dresses in worn, oversized pants and sportscoat with the belt cinched up entirely too far…just like grandpa.

Sure, we can figure out the weak links, guess the “alliances” and schisms within the gang before they show up. That’s what a “formulaic” genre picture is. We can figure out where this is going without being native Brits who remember the news stories.

But Oscar-winning director James Marsh (“Man on Wire,” “The Theory of Everything”), working from a Joe Penhall script, wisely limits the police point of view to nameless coppers doggedly burrowing through CCTV footage, hunting for clues.

This high-mileage/hard-mileage cast crackles and sells the conceit, that aged Brits — whom no one would suspect because Britain’s native-born criminal element long ago lost its initiative and its edge to “Albanians” and foreign imports — could pull this off.

And if only Winstone could Cockney his way through a proper mocking of somebody’s disguise — “That’s a proper ‘Uncle Fester, Send-in-the-Clowns’ whoopsie-daisy ‘ave an AWAY day, that is!” — only Caine could serve up the immensely quotable dialogue’s best summation.

“Crooks are like boxers. They lose their legs, first. Then they lose their reflexes. Then they lose their friends.”

Rating: R, for language (profanity)

Credits: Directed by James Marsh, scripted by Joe Penhall. A Lionsgate/Saban films release on Netflix.

Running time: 1:48