That it was a true story only came to me when the film ended and I saw the final card with Nigel Slater's picture. But, an interesting life doesn't make for a great film (or even a good one), if the story is not well-told.
The genre 'TV Movie' is right for this film, and that is where it should remain. It works at episodes strung together, watched at comfortable intervals. It's not 'appetising' film viewing.