Alex Etel, the child actor who upstaged Dame Judi Dench and Sir Michael Gambon in the TV drama Cranford, has wowed American critics in a film about the Loch Ness monster.

His co-star in The Water Horse is a computer-animated monster designed by the Oscar-winning company Weta Digital. Yet despite the brilliant special effects it is the performance of the 13-year-old that has had reviewers reaching for superlatives after the world premiere.

“Unlike some American child actors, Etel is winsome without being cloyingly cute,”The Hollywood Reporter wrote. “He holds the screen as commandingly as the young Roddy McDowall.”

In the film, adapted from a novel by Dick King-Smith, Alex plays Angus, a lonely boy whose life is transformed when he finds an egg on the lochside. When a baby monster emerges it takes over the child’s life, and the relationship between Angus and the pet that he calls Crusoe is the core of the film.

Because images of the monster had to be added to live action footage, Alex was often working alone on set, which he admits was a challenge. “The first thing you had to get over was the self-consciousness of it and that was really hard for me, especially in front of 200 people and a camera,” Alex told a press conference in New York.

He had to spend months apart from school friends because most of the shoot took place in New Zealand. He had swimming instruction, and some of the loch sequences required him to spend night sessions in a water tank. And then there was the challenge of learning a Scottish accent.

“All the action, the underwater scenes and then the accent on top of all that was a big, big challenge for me,” Alex said. He had worked with one of his accent coaches for just a week before he arrived in New Zealand, “which was just grasping the basics of it,” he said. “I had one for three months, she helped me a lot. The accent got easier, but it’s never going to be really easy because it’s such a distinct accent compared to mine.”

Alex was aged eight when he was discovered by Danny Boyle, the director of Trainspotting, who was casting his film Millions when he visited the school that Alex attended in Cheshire. As soon as he saw the boy, Boyle said: “That’s him; I’ll bet that’s him.”

Alex won the lead role and gave an astonishingly mature debut performance. His more recent success as Harry Gregson, the ragamuffin in the BBC costume drama Cranford, was his second professional outing.

Douglas Rae, the producer of The Water Horse, said. “Alex is a brilliant little actor. In Cranford, he shone as a wonderful new talent. Alex is completely intuitive and natural.”

The Water Horse is released across the US on Christmas Day, and in Edinburgh on January 19. But Alex was a baby when Rae first pitched the film to Harvey Weinstein, the founder of Miramax studios, in 1995. The project was shelved for ten years because of the costs of the special effects.

Alex said: “I would love to be an actor when I grow up. Anyone who has this opportunity and doesn’t follow it through would be pretty stupid.”

Explore Film

• Film Reviews

• Trailers

• DVD

• Oscars

• Cannes

Editor's choice

• U2 at Nou Camp Stadium, Barcelona
• The 50 Best Movie Villains
• The 15 golden rules of theatre etiquette