Because Alex Pettyfer was only 15 years old at the time of the film, he did not yet have a driver's licence, so the scripted car chase was changed to a horse chase.
Anthony Horowitz, author of the book, recommended Alex Pettyfer to play Alex Rider after seeing his impressive performance in the lead role in the British TV drama Tom Brown's Schooldays (2005).
The water tank holding the Portuguese Man-of-war Jellyfish was filled with 19,000 gallons of water. The jellyfish itself was a puppet.
The biggest, most expensive British independent film ever made up to that point.
Mickey Rourke accepted the role of Darrius Sayle because he wanted to hang out in the United Kingdom.