Rosemary Anne Sisson
Born in London in 1923. Prolific British scriptwriter, playwright and author, perhaps best known as one of the writers of the cult TV show Upstairs, Downstairs.
She seems to have had an interest in ponies with several of her scripts featuring horses, including episodes of the Follyfoot TV show, and both a film and TV adaptation of the James Aldridge book A Sporting Proposition (filmed as Ride a Wild Pony), as well as a 1970s TV drama adapted from Horse in the House by William Corbin. To find out more about these please visit the appropriate author's pages, or Rosemary's filmography link.
Rosemary also wrote the script for the Disney film about pit ponies, Escape From the Dark, which she then adapted into a novel.
Her novels are mainly historical, and I think the adaptation of the Disney film was her only pony related one. She did write a play called The Dark Horse, but I think this is a general historical story and nothing to do with horses.