Great family film. Next cheapest is £4.95 @ Dvd,co.uk. Also 9% cashback through Quidco.
When their father (Michael Kitchen) is imprisoned after being falsely accused of spying, young Bobbie, Peter and Phyllis are forced to move to Yorkshire with their mother (Jenny Agutter, who played Bobbie in the 1968 film version). The local railway provides a useful focus for them, and they strike up a friendship with an elderly gentleman (Richard Attenborough) who vows to help them prove their father's innocence.