‘Lady in the Van’: Maggie Smith a long way from ‘Downton Abbey’

So here’s Dame Maggie Smith in her ninth decade, still running thespian circles around most actors half or a third or dare we say a quarter of her age.

Having recently wrapped her magnificent run as the snooty, old-money Dowager Countess in the much-adored “Downton Abbey” TV series, Smith gives an equally delightful performance as a seemingly half-mad homeless woman who avoids bathing, yells at children, tells endless tall tales and often can’t be bothered with going inside to use the bathroom.

Smith is literally “The Lady in the Van,” Nicholas Hytner’s self-consciously artsy and somewhat slight but tartly funny and occasionally wise adaptation of Alan Bennett’s play of the same name. (In fact, Smith played this same part in a stage production in 1999, and in a BBC radio play in 2009.)

The story, we’re told, is rooted firmly in Bennett’s own life. One day in the 1970s, a stubborn, beyond eccentric, often ill-tempered old lady named Mary Shepherd parked her dilapidated, overstuffed old van in front of Bennett’s North London home, was eventually allowed to park in Bennett’s driveway — and stayed there some 15 years.

In an interesting dramatic conceit I sometimes found more cloying and obvious than clever, we get two versions of Alan Bennett, both played by Alex Jennings, who gives two fine performances. (Given today’s movie-magic technology, both versions appear onscreen at the same time, seemingly talking with one another and interacting with each other, and it doesn’t feel the least bit faked.)

One Alan Bennett is the man experiencing his own life, whether he’s conversing with neighbors who aren’t shy about telling him they were underwhelmed by his latest play, dealing with Mary’s latest outrageous antics or tending to his aging and ailing mother.

The other Alan Bennett is the writer who takes a step back from every breathing moment of his life and considers its potential as possible material.

Often, the two Alans are at odds with one another. They’re like twee, intellectual, Brit versions of the angel and the devil on Pinto’s shoulders in “National Lampoon’s Animal House,” as Pinto considers whether to take advantage of a passed-out teenager. (Now THERE’S a scene that probably wouldn’t make the final cut of a movie made in 2016.)

Alan is not allowed inside Mary’s van, which is crammed to the roof with old newspapers, soiled clothes, knick-knacks and some substances too foul to mention. But every time she kicks open the doors to claim she’s dying or to terrorize the neighborhood children or make some outlandish claim about her life’s adventures, Alan gets a glimpse inside that van and a glimpse inside Mary’s life, real and/or imagined. He becomes fascinated by her and perhaps even grows fond of her.

As Smith did in “Abbey,” she takes a character we probably wouldn’t want to spend much time with in real life and turns her into someone we thoroughly enjoy onscreen — especially when she’s calling out members of polite society on their B.S., or allowing us to see just a faded but still shining glimmer of the woman she once was, a woman whose heart once might have been bursting with a love for life.

There’s more than a hint of darkness in “The Lady in the Van.” The great Jim Broadbent drops in as a mysterious stranger with no good intentions. At the very start of the film, we see blood on the van’s windshield, and I’ll say no more.

Mostly, though, “The Lady in the Van” is about a talented young writer still wrestling with how to draw upon his own experiences without exploiting others — and it’s about the boundless talents of Maggie Smith, sometimes chewing up the screen, sometimes saying volumes simply by sitting very, very still, with a perfectly perfect expression on her face.

[s3r star=3/4]

Sony Pictures Classics presents a film directed by Nicholas Hytner and written by Alan Bennett. Running time: 103 minutes. Rated PG-13 (for a brief unsettling image). Opens Friday at local theaters.