Author and screenwriter Anthony Horowitz natters at a pace similar to one of his plots - his words bursting out like a machine gun. Then, just as suddenly, it stops, as if the magazine had been emptied abruptly.
Horowitz brims with a youthful enthusiasm that seems slightly at odds with his 55 years, although he easily looks 10 years younger with his boyish face.
Clearly, such qualities have helped him attract a horde of teenage fans. Many will recognise him as the creator of the successful Alex Rider novels, named after the teenage spy the series is centred on, one of which leaped onto the screen in the 2006 movie, Stormbreaker.
Others will know him for Necropolis, the fourth novel in his Power of Five fantasy series, recently released in paperback. It is set partly in Hong Kong, which holds a special place in Horowitz's memories because this is where he married his wife, Jill, 22 years ago.
'We chose Hong Kong because all the registry offices we wanted to get married in London were booked up,' he says with a shrug.
On a visit to meet fans at the annual Book Fair, Horowitz says that as an outsider, he found Hong Kong intriguing because it struck him as a 'bubble' environment.
'How do you leave it?' he ponders. 'You can fly and get on a boat, but still there's a feeling of it being like a prison.''
In other words, it's perfect as a setting for Necropolis, which features Victoria Prison cast in a sinister light, and an evil posse of characters called the Old Ones, who are out to destroy the world. Four teens known as 'the gatekeepers' come to the rescue, and the result, according to one enthusiastic reviewer, is 'an excellent, fast-paced thriller, ideal for boys but equally enjoyable for girls'.
The city's teeming crowds also help add another dimension to his fictional worlds.
'How many people can vanish here?' he wonders. 'If 10,000 people disappeared, who would notice? I don't think writing about it could work anywhere else.'
Warming to the subject, Horowitz says the cityscape provides rich material for the high-octane action sequences and plot twists that anchor his novels.
'It has a lot to offer. There are the high-rises, the hustle of the traffic, what's going on in the harbour ...,' he says.
'I remember once being in a market off Hollywood Road and seeing a fish suddenly sliced in half. It was still alive and the heart still beating. That single image said more to me about Hong Kong than five careful paragraphs of prose in a guidebook and by that I don't just mean 'yuk'.
'I might see something such as a building site with buckets being hoisted up and down. Then I could think it'd be quite fun for a bloke to jump off a roof. That'll stay with me for a couple of years until a character such as Alex is on a roof.'
Horowitz reckons part of the appeal of his novels is that they are written for a generation that is visual and technological.
Yet while he knew as a child that he wanted to write, Horowitz says he never set out to write for youngsters. He has a successful parallel career as a television writer, adapting Agatha Christie's Poirot stories and creating thrillers such as Foyle's War and Midsomer Murders for the small screen, and has written novels such as The Killing Joke for adults.
'It's a mystery to me how it happened,' he says of writing for teens.
'One day it was raining and I was quite bored and it went from there. I like narration, pace and flow and youngsters' books are perfect for that. With adult books, it might take 20 pages while in a kids' book you can just go for the jugular.'
Having forthright feedback from his young fans helps keep him on his toes. 'They're very quick to get bored. If they love it they embrace it or it's 'get lost',' he says with a laugh.
Horowitz's 19-year-old son, Cassian, who accompanied him to Hong Kong, is among his most outspoken readers.
'It's important to have someone like that,' says Horowitz. '[Cassian] is a very good critic.'
Although he has been invited to talk about his writing, Horowitz doesn't see himself as a literary talent.
'I'm a story-teller but I don't think I'm a great writer,' he says. 'I'm an entertainer and passionate about my work. I work very hard. Writing is 90 per cent of my life.'
Unlike some writers who adopt a disciplined schedule, Horowitz says there is no special rhythm to his writing.
On a good day, he might produce 3,500 words, equivalent to a chapter. On others, the output is more like a couple of paragraphs.
Reading and writing has been a part of his life since he was in primary school. He grew up in a wealthy Jewish family in north London, and 'it wasn't a particularly happy time', he says.
'There wasn't much emotion and it was what you might call a retro lifestyle in that gongs sounded for dinner. So reading and writing became my lifeline, if you like.'
His first 10 books helped channel his negative feelings of that childhood, he says, and became a bridge to Alex Rider and his other literary output.
'They weren't bad books but they were very north London rich Jewish boy. Then I redirected myself to more universal tales,' says Horowitz, who is now working on the final novel in his Power of Five series.
So, might Hong Kong make a return? 'No. It's been done,' he says resolutely.
Then as an afterthought, his face lights up and he grins.
'But Alex could come to Hong Kong. I'd happily send him here. It's such a super place.'