First night: War Horse, Odeon Leicester Square, London

The work comes to our screens having lost its main star from the stage. The wooden puppet that wowed theatre audiences has been abandoned as Steven Spielberg adds realism but loses some of the magic in his adaptation of Michael Morpurgo's novel.

The equine star was walked down the red carpet of the London premiere last night, highlighting the soon-obvious screen fact that, apart from running and neighing, horses don't have much in the way of winning expressions to endear them to us on the big screen. Despite the efforts of the ensemble, it's a hurdle that the action never manages to jump.

With a screenplay written by the Four Weddings and a Funeral and Notting Hill scribe Richard Curtis and Billy Elliot's Lee Hall, and directed by Spielberg, it was inevitable that the action would concentrate on the sentimental. Alas, the thin line between sentimentality and schmaltz is all too often crossed.

Partially on a whim and in a show of male bravado, Ted (Peter Mullan), a farmer, outbids his landlord (David Thewlis) using his rent money to pay for a thoroughbred in an auction in the local Devon village. His wife, Rose (Emily Watson), is distraught when her alcoholic husband returns home without a carthorse to work the land.

Their son Albert (Jeremy Irvine) takes it upon himself to train the thoroughbred, Joey, to plough, and so begins their unbreakable bond. The vistas are dazzling, with the vibrant hues adding a genteel British period drama air to the proceedings. The tone changes when harsh finances lead Ted to sell Joey to the Army. Determined to see his horse again, Albert enlists. Given that Spielberg was the director behind some of the greatest war scenes committed to celluloid in Saving Private Ryan, it's perhaps no surprise that the best scenes are those that take place in the midst of the First World War – men suffering in trenches and horses trampling through barbed wire while bullets fly over their bewildered heads.

Nonetheless this screen adaptation accentuates the episodic nature of the source material. Joey is passed through a succession of owners, British, German and French, and the series of cameos starts to get tiresome after Niels Arestrup's arresting turn as an old Frenchman trying to protect his granddaughter from the ravages of war. Other characters simply don't get enough screen time.

As is Spielberg's habit, the final act descends into slush. The reliance on chance and coincidence and the Gone with the Wind sunsets add to the feeling that this is a tale best watched on stage.