FEW films in recent memory have demanded a big screen as much as this high-fantasy adaptation. It compensates for a fairly generic hero story beating at its heart by giving us good mythologising and just being the biggest in the room.

It is based on the 2001 young adult steampunk novel series by Philip Reeve and events takes place hundreds of years in the future.

Humanity has all but completely fallen thanks to the Sixty Minute War, in which a series of quantum bombs were set off that left the world a wasteland where resources are scarce. To survive and assert dominance, humankind came up with the idea of making the world’s great cities into mobile machines that traverse the land in perpetual war with one another. The larger cities “absorb” smaller surrounding communities whose on-board societies live hearing stories of, and scavenging old tech (iPhones, computers, toasters) from, a time gone by.

Our hero is an enigmatic young woman named Hester (Hera Hilmar). She boards the almighty London to exact revenge against leader Thaddeus Valentine (Hugo Weaving), whom she blames for the death of her mother. There she meets wide-eyed Tom (Robert Sheehan) and, after they are forced into the wilderness, band together in a larger fight. The idea of mechanised cities roaming the Earth is a bold concept indeed, and it takes some time to convince. However, it gets there thanks to a nice, tangible sense of world-building (despite its CGI-heavy aesthetic) and an eye-popping epic scale.

The film’s greatest strength is the sheer size of it; these humongous mechanical cities, with ever-moving parts and on ground-shaking wheels, are a sight to behold. It’s a spectacle that does a lot of the heavy-lifting, so to speak, as the quest that propels the story forward leans on the familiar and doesn’t have a great deal of chemistry to speak of between the two leads; Sheehan has a fairly thankless, put-upon role compared to Hilmar’s more action-packed one.

Directed by first-timer Christian Rivers – a former storyboard artist talent nurtured by the film’s long-time developing producer/co-writer Peter Jackson – it also works solidly on its own terms as an escapist yarn propped up by an imaginative and intriguing mythology that feels lived-in and “believable” as far as these things go.

It has flaws to spare, not least an over-reliance on a pedestrian hero arc bolted on to a quite standard adventure story. But it’s fairly rewarding in its sense of immersion in a well-designed world of towering scale that reminds us why the big screen is referred to as such.