Dame Maggie Smith is to star in the film adaptation of Alan Bennett's play The Lady in The Van.

The play has been a hit in the West End and tells the autobiographical story of an elderly lady who took refuge in the author's garden.

Smith, a star of Downton Abbey, will play pensioner Miss Shepherd, who lived on Bennett's driveway for 15 years.

Alex Jennings will play Bennett in the film, which is set to be released late next year.