An orphaned girl named Sophie (Ruby Barnhill) is kidnapped by a mysterious giant (Mark Rylance) and transported to ‘giant country’, where he plans to keep her captive to prevent the human world from learning of his existence. When Sophie sees the giant getting bullied by his larger and more destructive neighbours, she tries to help him fight back.

The BFG, a 1982 novel by noted children’s author Roald Dahl, was adapted last year as a live-action feature film thanks to screenwriter Melissa Matheson (The Black Stallion, E.T.) and director Steven Spielberg. In many respects it seemed a match made in heaven: one of the world’s best children’s authors paired with a gifted screenwriter (who sadly passed away before the film was made) and a legendary director. In practice, however, The BFG feels a bit of a struggle. It boasts a marvellous list of ingredients, but they do not quite gel together. The result is a film that entertains, but only to a certain extent.

A big problem is with the story, which arguably hews too closely to the novel and therefore adapts its own biggest weaknesses. The BFG was always a delightful story with a rather unconvincing climax, and it is a surprise to see that climax broadly retained here with all of its faults intact. It feels weird to write it, but this is one case where a film could have actually taken the more egregious liberties with an adaptation for which Hollywood is infamous.

The story weaknesses are a shame, because the world that is built and presented here is a delight. The colour palette is brighter and more vivid than I have ever seen used by Spielberg and his cinematographer Janusz Kaminski. The production design is utterly charming, and successfully captures a sort of cozy British feel that is usually quite alien to American filmmakers.

Mark Rylance does a superb job as the Big Friendly Giant, with his own performance complemented by some generally excellent computer-generated animation. Ruby Barnhill is enormously appealing as Sophie, although that is hardly surprising: if Spielberg has demonstrated anything over the course of his 40-odd year career it is that he is a master at drawing strong performances out of child actors. Their performances seal a genuinely wonderful relationship between the two characters. It is why the film’s first two acts, which focus almost solely upon their developing friendship, work so brilliantly and why the climax, which necessitates broadening the film’s scope, feels flat by comparison.

If anything more is needed from their relationship. The film introduces a plot thread of an earlier human child living with the BFG, but it is a thread that ultimately feels undeveloped. A lot of potential gets left on the table, and because that potential is visible to the audience it sometimes makes the film feel a little less accomplished than it probably is.

The BFG is an enjoyable fantasy film for children and families, but at the same time it never shakes the feeling of being a missed opportunity – and that a better and bolder adaptation has remained annoyingly out of reach. For Steven Spielberg it feels like a minor work: oddly out of synch with his more recent dramas and sub-standard to the blockbuster hits in his past. I suspect history will not remember this film particularly well.