Alex Rider (played by big-screen newcomer Alex Pettyfer) is a 14-year-old at a well-to-do West London school who finds himself recruited by MI6 when his uncle (Ewan McGregor) dies in mysterious circumstances while returning from a mission in Cornwall. To his dismay, Alex realises that he has been groomed for special service by his late uncle: proficient in a variety of life-saving and death-defying skills, he is a superspy-in-waiting, and Alan Blunt (Bill Nighy) and Mrs. Jones (Sophie Okonedo) need him to carry on the assignment. So Alex finds himself undercover in the lair of business tycoon Darrius Sayle (Mickey Rourke), who is preparing to launch the top-class Stormbreaker computers in British schools. It seems Darrius has a dastardly plan up his sleeve –but what could it be? And can Alex save the day?

The Alex Rider novels, written by Anthony Horowitz, are aimed at young readers, and the film of Stormbreaker is a no-nonsense PG-rated affair. Full of action and adventure, and putting its hero through his paces, it nonetheless keeps itself family-friendly. Audiences, young and not so young, might find this a tad frustrating – after all, James Bond himself has been entertaining kids for years. But there’s clearly an appealing fantasy here of a schoolboy having to bluff his way through a hi-tech computer plant or wrestle with a nasty-looking squid. Then there’s Stephen Fry’s weapons expert Mr. Smithers – a Q-like figure, obviously – who dispenses teen-friendly gadgets from the back of Hamleys. Horowitz’s screenplay wears all of these elements lightly, and as a result Stormbreaker is about an hour shorter than an average Harry Potter movie.

Comparisons with Potter are natural – both stem from blockbuster books, both feature best-of-British cast, and both heroes make novel use of London train stations: if King’s Cross is where Harry Potter catches his train, then for Alex Liverpool Street houses the underground MI6 office space. ‘What is this place – Hogwarts?’ he asks. Well, no, it isn’t – and Alex Rider might not become as successful a franchise as the trainee wizard. For one thing, the appeal is narrower: boys of all ages can enjoy a good espionage tale, but the genre has always lacked decent female characters for audiences to relate to. And although Harry is a more fantastical character, he gets to practice his craft in that most universal of settings – secondary school – while the ostensibly engaging Alex is taken out of his element and sent off to do stuff which most of us will never be able to identify with directly.

In Stormbreaker‘s favour, however, is a beautifully glossy look which shows us a London generally ignored by filmmakers – brilliant, modern, with its stunning river and skyline – the London we see around us every day. And, notably for a bona fide British film, Stormbreaker, as directed by Geoffrey Sax, is untouched by cinematic coyness or clumsiness: confident without having attitude, it tells its story with a smile, happy to be a movie, feeling no need to apologise for not being a novel, a play, or even a television programme. If the directing can occasionally be a little over-eager, on the whole it strikes the right tone, playing the story straight but not taking itself too seriously – which is why Bill Nighy comes across as a little too arch on this occasion.

Thankfully, Pettyfer makes for an appealingly pensive and subdued lead. Some reviews have had it that he is too bland, or too pretty, for the role of the novice spy, but Alex Rider is a reluctant recruit – he doesn’t set out to be a hero, and he plays his cards close to his chest. Pettyfer’s poise is impressive, and he has a lot to do in a story that affords him scarcely a moment of light relief. If he doesn’t star in the next Alex Rider film – and reports suggest he won’t, as he may already be too old to play the mid-teen again – then it’s a shame, as Stormbreaker feels very much like the first instalment in what could be a winning franchise, and Pettyfer would deserve the chance to grow into the part.

Whatever the future holds, Stormbreaker is the breeze that this very hot summer has needed, and London itself looks good enough to host the Olympics.