Dodie Smith's endearing heroine Cassandra Mortmain, a girl on the brink of womanhood, resides with her eccentric family in a dilapidated Suffolk castle, and details their impoverished, unconventional life in her journal. Romola Garai's Cassie is a memorable combination of pragmatism, youthful awkwardness and wistful fascination with the adult world. She carries the film, but what else is there? Nighy as the grumpy, distant father, a once-acclaimed writer struggling to start his second book; Fitzgerald as bohemian stepmother Topaz, a former artist's muse; plus an Austen-style narrative involving elder sister Rose and a wealthy American and his brother - the heirs of the castle, who come to stay on the estate. Could they be the answer to the family's problems? A BBC co-production with all the right credentials, this is an entertaining enough 1930s period piece, pretty in a 'dappled golden light and Debussy' way, gently humorous in places, and with a broader appeal than just the teenage girl market. But it rarely looks or feels like big-screen material.