For six seasons Dame Maggie Smith has been delighting television viewers as dowager Violet Crawley in the Downton Abbey shows. Younger fans might be unaware that she’s won Oscars twice (for California Suite and The Prime of Miss Jean Brodie) and has had an illustrious career prior to appearing in the hit PBS series.

In The Lady in the Van, she’s been cast as a character who is the opposite of the imperious aristocrat of Downton Abbey. In the film, Margaret Shepherd is a down-and-out homeless woman living in a van that she parks on the street in the Camden Town section of North London.

At the point of departure in the early 70s, we learn that Margaret’s plight is one of her own making. She’s been on the run for five years after leaving the scene of a fatal hit-and-run car accident.

Although the devout Catholic has confessed the sin to her priest, she could never bring herself to surrender to the authorities. Consequently, she’s forever looking over her shoulder, fearful that her arrest might be imminent.

The plot thickens when she can’t afford to fix her jalopy that is sorely in need of a tune-up. Most of the residents in the upscale neighborhood where the van is sitting would like to see the eyesore towed away.

However, Alan Bennett (Alex Jennings) feels compassion for the overwhelmed octagenarian, perhaps because his own mother is about the same age as Margaret. So, against his better judgment, the famous Tony Award winning playwright allows “Miss Shepherd” to park her disabled car in the driveway on the express understanding that the arrangement is temporary.

However, to his dismay, Margaret ends up squatting on his property for the next 15 years. Can the odd pair coexist peacefully?

That is the question at the heart of The Lady in the Van, a heartwarming dramatic comedy inspired by actual events. The film was adapted from Bennett’s 1999 theatrical production of the same name which also starred Maggie Smith.

Smith looks relaxed onscreen in the role she originated onstage, whether cadging for alms or exhibiting pangs of remorse about the accident that caused her problems. Just as effective is Alex Jennings’s interpretation of Bennett as a conflicted soul who is constantly carrying on an inner dialogue with himself.

Excellent (****). Rated PG-13 for a disturbing image. Running time: 104 minutes. Distributor: Sony Pictures Classics.