War Horse is not a film that has immediate impact but rather one that's message grows and strengthens with time. A comment on the futility of conflict it also tells of the courage, spirit and selflessness of people and animals facing impossible odds.

St Albans-born author Michael Morpurgo is in a lighthearted mood after last night's UK premiere attended by the Duke and Duchess of Cambridge and his levity is infectious. Despite the seriousness of the subject matter, it is comforting to hear how happy he is with Steven Spielberg's magestic adaptation of his book.

"He's kept close to the spirit of the book," says Michael. "I hope the experience leaves you desperately sad, wrecked really because of the horrors of World War One. The charge scene, where we're looking down on the battlefield and seeing the horses and men lying there is all that needs to be said. The pity. The waste.

"Any story you write about war is going to be political. I'm a war baby. I grew up in London after the Second World War and one of my earliest memories is of the city in ruins.

"You come out of that cinema or read that book or see it in the theatre and anything that gets us asking the question why? Was it necessary? Anything that gets us thinking, particularly for young people is really important."

Filmed in Luton Hoo and with horse and riding training for the actors taking place in Rickmansworth, War Horse is a truly British film. The most completely British movie Spielberg says he's ever made.

More on this in tomorrow's St Albans Review and Friday's Watford Observer.