There is, of course, rather more to his appeal than the bald fact of his nationality. In the appropriately showbizzy surroundings of the Brasserie at the Cafe Royal in London's West End - all busts of George Bernard Shaw and signed photos of black-and-white luvvies - a clean-shaven David Suchet ponders the enduring popularity of his moustachioed alter ego.
"On the page, you know, he's a bit of a prig," he says. "I've often wondered, reading the stories, what it is about this strange, almost obsessive little Belgian, who believes he's the world's greatest detective and has the ego the size of a big city, that made him so attractive to a readership that wouldn't give him up - and turned Agatha Christie into the top-selling author of her day. What is it that made people say, `I really like this man' rather than `I can't bear him'? It took me a long time to realise that it was his very eccentricity of character that appealed to the British so much. On top of that, they liked his desire to do good and rid the world of crime, his attitude of being a Harley Street specialist in his own field, his humour, his malapropisms, his dapperness, his running-down of the English upper classes and his standing up for his own nation." Phew.
Suchet, really getting into his stride now, continues: "Agatha always wrote of him as having a twinkle in his eye. So he was aware of himself and almost parodying himself as well." It is this twinkle that really distinguishes Suchet's performance. Dressed in an immaculate grey three- piece suit with matching hat and gloves and carrying a cane topped with a silver swan, his Poirot can sprinkle even the most apparently po-faced words with his own brand of actorly fairy-dust. So, in Suchet's mouth, a line such as Poirot's peremptory dismissal of the game of golf - "to hit a little ball into a little hole in the middle of a large open field, I think it is not to the taste of Poirot" - raises a smile rather than a scowl. His awkward English syntax only serves to enhance his charm.
Some critics have attacked the cosy safety of period drama, but Suchet leaps to its defence. "It's great escapism into a world that's disappeared," he asserts. "People enjoy seeing a recreation of something that has gone out of fashion. If you watch a wonderful programme like Cracker, you see that the style has moved on, but then it would, wouldn't it? These were written 60 years ago. Poirot is not modern television, it has never tried to be modern television. It is faithful to a period that is out of date."
Another accusation levelled at Agatha Christie is that her plotting is too predictable. "There is a formula to her stories," Suchet concedes. "In filming the stories, I knew where they were all going to go in the end. They follow a pattern, but I think people feel comfortable with that. Some people have bets going about whodunit, and then tune in for the summing-up. I've never seen any of the money, though."
Suchet is also well-practised in fending off the argument that we are overdosing on telly 'tecs. "That's a fair criticism. At one stage there was Poirot, Morse, Frost, Murder She Wrote - it seemed there was one for every night of the week. But people love whodunits. People love to guess. Some people say to me, `Viewers just sit and watch television mindlessly', but they're underestimating the audience. I've been in the business 27 years, and to judge from my mail-bag, there are some great viewers out there who want stimulation and who want to be intellectually excited. High ratings doesn't necessarily equal merit."
In six years, LWT have produced 50 hours' worth of Poirot and sold them to 55 countries. But Suchet is not yet ready to hang up his moustache. With a Poirot-esque twinkle, he tells me that there are still 24 stories they haven't yet filmed.
`Agatha Christie's Poirot', Sun 8pm ITV.
Two further Poirot stories will be broadcast in the New Year