SHORTLY after the digitally-rendered dust settles on an eye-popping action sequence which opens Mortal Engines, the thorny issue of Brexit ripples thousands of years into our desolate future.

"Going into Europe – biggest mistake we ever made," despairs the Mayor of London (Patrick Malahide) as he surveys a post-apocalyptic wasteland dotted with motorised cities mounted on caterpillar tracks.

Adapted from the novel by Philip Reeve, Christian Rivers' rollicking action adventure doesn't stoke that political fire any further but does make a few missteps over the course of two breathlessly enjoyable hours.

The script penned by Fran Walsh, Philippa Boyens and Peter Jackson – engineers of The Lord Of The Rings trilogy – idles in first gear for the initial 20 minutes and grinds through clunky interludes.

More than once, first-time director Rivers falls back on his Oscar-winning background as a visual effects supervisor and allows spectacle to trump substance, aided by a vivid steampunk aesthetic.

Mortal Engines is bolted together from the first book of a four-part odyssey. Survivors huddle on mobile metropolises fashioned from scavenged parts that 'ingest' the resources of rival cities to feed roaring furnaces.

The largest of these behemoths is London, commanded by Mayor Magnus Crome with guidance from noted academic Thaddeus Valentine (Hugo Weaving).

Masked assassin Hester Shaw (Hera Hilmar) sneaks aboard London and attempts to assassinate Valentine. Apprentice historian Tom Natsworthy (Robert Sheehan) intervenes and during the subsequent chase he tumbles off a gangway and regains consciousness next to Hester in the wilderness.

The fugitives are forced to work together as they encounter famed pilot Anna Fang (Jihae) and a half-human, half-machine warrior called Shrike (Stephen Lang), whose past is inextricably entwined with the girl.

Hilmar is an appealingly spunky heroine and verbal rat-a-tat with Sheehan's apprentice aviator allows the darling buds of romance to appear gradually in lands poisoned by humanity's greed. But it is Lang's moving performance that sows the seeds of the film's most intriguing and emotionally rich on-screen relationship. Shrike is the most heartbreakingly 'mortal engine' on display. He is the tormented ghost in the precision engineered machine.

RATING: 6.5/10