Hinted at is some kind of an earlier accident involving the van, blood on the windscreen, and avoidance of the police.
Which may be why, from time to time, Miss Shepherd has a mysterious menacing visitor, who seems to be demanding money. The residents of the respectable street respond with British reserve, occasionally proffering gifts of food which are greeted by truculence. They may not be thrilled by her presence, but something stops them from insisting that she move on.
When, however, the authorities mark the street with yellow lines, Miss Shepherd realises that she either secures off-street parking, or she will have to move on.
Alan Bennett offers her a temporary solution – the use of his driveway "for a month or two".
Some thirteen years later, she is still there.
Bennett (who wrote the play on which this film is based) is unflinching in his depiction of himself, as a shy, reclusive bachelor, who sees himself as almost two people – the one who deals with everyday life as best he can, and the one who chronicles said life in books, articles, and plays.
In the film we see the two personae involved throughout in an uneasy dialogue.
Meanwhile we learn more about Bennett, through the dialogue, through seeing him at work in the theatre, and in his interaction with Miss Shepherd and their neighbours.
Miss Shepherd ages, and not well. She changes her van, acquires a three wheeler car (probably uninsured) and paints both a gaudy yellow. Enter a social worker, complete with forms, professional patter and a determination to fit Bennett and Miss Shepherd into her structures. (They are determined not to)
Bennett is horrified by the thought that, in the social worker's eyes, he is her carer. He is also trying to come to terms with his own aged mother's increasing problems with dementia.
Layer by layer this slow moving saga develops, as we learn about Miss Shepherd's tragic past, and realise that her seclusion and her truculence are her attempts to protect herself from incarceration, whether as a result of the mysterious road accident, or through being institutionalised "for her own protection". Comic and tragic both is the awareness of Miss Shepherd's increasingly repulsive body odours, so convincingly depicted that the audience at times gave murmurs of repulsion.
The slowly moving plot could have been so understated as to be underwhelming.
However Maggie Smith's superb depiction of an old woman's determination to maintain her dignity and what remains of her sanity while struggling against her demons, and Bennett's unflinching portrait of a reclusive artist keeping his distance for over a decade, yet clearly protective of the cuckoo in his nest, make this a memorable movie.
A bonus is the insight into Bennett's creative life, and his wonderful prose brings an edge and a subtlety to the dialogue.
Under the humour, the reserve and the repulsion is a portrait of a kind of caring, and of the difficulty of forgiveness, not only of exploiters, but of oneself.
Like most of Bennett's work, this movie could be seen again and again.