Adapted from Alan Bennett’s book, which in turn was adapted into an award-winning play by the man himself, The Lady In The Van is a likeable low key 'Odd Couple' comedy-drama that leans on Maggie Smith’s newfound penchant for the acerbic asides. Downton and Marigold Hotel fans won’t be disappointed with their favourite actor here.

"One seldom was able to do her a good turn without thoughts of strangulation." Mary Shepherd (Smith, who also played the role in the play) is a homeless grouchy kook living in her clapped-out van on a quiet Camden street in North London in the seventies. Almost adopted by the street (she’s brought crème brúlée, given Christmas presents, and stubborn jam jars are prized open - each offering batted off without a thank you) there are only a few mutterings of complaint from the residents when she puts the van in gear and decamps in front of their homes. When she settles across the street from playwright Alan Bennett (Jennings, The Queen) the two strike up an unlikely friendship which leads to Shepherd moving the van into his drive for a short stay. That short stay turns out to be fifteen years...

While keeping things light and frothy, Bennett’s screenplay resists the urge to get too warm and cosy. Bennett never invites Shepherd inside and the slow creep of respect both have for each other is neatly dealt with. However, director Nicholas Hytner (who has already two Bennett adaptions under his belt - The Madness of King George and The History Boys) avoids including any awkward dead of winter scenes with Smith shivering in her van, which wouldn’t help Bennett’s likeability and there seems to be an importance on finding him likeable.

The attention will be on Smith and there will be rumblings of an Oscar nomination but it's Alex Jenning’s performance that catches the eye too as, of course, he is playing two characters. Jostling for position while Bennett and Shepherd enjoy their fractious relationship is Alan Bennett’s alter ego - Alan Bennett - and both politely bicker over their craft and what to do with the problem in the driveway. It also branches out to include Bennett’s mother (Gwen Taylor) who slowly succumbs to dementia.

While these moments are in themselves enjoyable they are distractions from the Smith-Jennings dynamic; the latter subplot does nicely mirrors Bennett’s relationship with his demanding mother, the former’s meta tactic snaps one out of the story just when one should be engrossed. And both take up room where there was a deeper story to explore: in the opening scene Shepherd was involved in a hit-and-run in the sixties and spends her remaining years living in fear of capture. Broadbent was the constable giving chase and, knowing her secret, turns up once in a while to accept hush money. However, this gets lost and is a glaring loose end.

There comes a point too where the story gets stuck in a holding pattern with repetitive scenarios - Bennett does Shepherd a favour/Shepherd doesn’t say thank you,/Bennett grumbles - but it rallies for a touching ending that again refuses to lay on the sentiment thick.