David Suchet: Poirot and me

David Suchet likes to think of life as a spider's web. The spider, you see, spins his web from behind; he can't see what he's creating. "The only time he can check what led to what is when he turns around," says Suchet pensively. "So in our life. We don't know what we're spinning, what we touch, what we do…"

It's a philosophy that is particularly on his mind today. Twenty-five years ago, Suchet was asked to play Agatha Christie's fussy little Belgian detective, Hercule Poirot, in an ITV drama series set eternally in his late-1930s world. Suchet's brother John, the ITV newsreader, warned him off the role – "I wouldn't touch it with a barge pole," he told him, "It's not you at all" – and Suchet himself hadn't read any of the books. But he agreed. And next week, as Poirot solves his final case on ITV, Suchet will say adieu to the character who has become the defining – and best-loved – figure of his career.

He has solved the ABC Murders. He has unravelled the Mysterious Affair at Styles. He has witnessed Death on the Nile. In the final series of dramas, surrounded by their typically acute period detail, Poirot is ageing, and there is one more death that we know he cannot escape. Today, as Suchet looks out on a grey, mizzly skyline from the 14th floor of ITV's studios on Southbank, the city is in a suitably sombre mood. "I haven't fully mourned him yet," says Suchet gently. "I suppose that will come. And I will miss him from my life until I die. But everybody has their time. And this is his."

Even without the luxurious moustache and the perfectly brushed homburg, Suchet is unmistakable, dressed tidily in a blue shirt, a wine-coloured waistcoat and dark jeans. He is, of course, a little leaner than his famous TV creation – that famous silhouette is 50% padding – and his voice is far deeper; he is capable of an expansive, carrying laugh that would doubtless raise a disapproving eyebrow from his fictional counterpart.

A few actors have become, like Suchet, the living embodiment of a literary detective. John Thaw did it with Inspector Morse; Raymond Burr did it with Perry Mason. Jeremy Brett's Sherlock Holmes has his champions, while my mother maintains that Miss Marple should have been officially retired from the television after Joan Hickson's definitive depiction. But none can claim the longevity of Suchet's Poirot. Morse, which seemed to run forever, actually consisted of only 33 episodes: when Curtain airs, Suchet will have completed the entire Poirot canon, committing 70 novels and short stories to camera. (Christie pedants are welcome to quibble that one very short story, the Lemesurier Inheritance, and the posthumous Capture of Cerberus, went unfilmed.)

Suchet remains in character between takes, in an attempt to inhabit the character as fully as he can, and in his new book, Poirot and Me, he admits that it became hard, at times, to know where the mustachioed detective ended and where he began. And while Poirot is famous for the deductive brilliance of his "little grey cells", he is also unique for his idiosyncrasies: are there traits in particular that they share?

"Well, I do like to be precise," says Suchet. "I don't like seeing crooked pictures. I like seeing things in order; I do like symmetry. I hope, though, that I'm not as obsessive as he is." Poirot has been known to refuse to eat boiled eggs that aren't the same size as each other. "I believe these days that would be classed as OCD."

Talk to anyone who has acted with David Suchet and the one word you repeatedly hear is "meticulous"; his co-stars marvel at the preparation that enables him to memorise the 10-minute-long denouements, in which Poirot painstakingly reveals the killer, and perform them in a single take. There is a suggestion, in his own book, that Suchet's dedication to the part, his perfectionist attention to detail, has not always made him the easiest man to work with. There are stories of him refusing to wear certain suits, and an early, decisive piece of brinkmanship over the correct way to sit on a bench.

"When it comes to fighting for a role in the way that I want to play it, I'm afraid I'm not that easy," he admits. "I have never liked directors telling me how to play a role. Ever."

By the later series of the show Suchet was an executive producer, with considerable creative power. I can imagine him, I say, being a tough man to negotiate with. "I don't wish to cause anybody hurt or harm," he says a little penitently, "but I think there will be directors who have had a very difficult time with me. And I apologise to them now."

Still, you'd have to say that it's been worth it. In my family, where the murder mystery is considered pretty much the acme of television, and where dinners are regularly punctuated by the horrified screams of some old ham discovering a body in the bushes, Poirot has always stood apart for its high production values and the calibre of its actors. What other whodunnit can boast Damian Lewis, Russell Tovey and Christopher Eccleston before they were famous? And you certainly wouldn't see Michael Fassbender turning in a typically nuanced performance – like the one he gave in After the Funeral – in Midsomer Murders.

Christie's plots, in which death visits the village fete and heiresses lose the family jewels, can of course look ludicrously quaint against the modern diet of Scandi-noir or the endless slew of American forensics. But in a world of angst-ridden, morally compromised crime busters, the robust egotism and moral rectitude of Hercule Poirot are almost a comfort. "He has a great humanity, which I would like more of," says Suchet. "A love of people. And a sense of right. He won't do what he believes is wrong, and I think the audience likes that."

The proof is in the fan mail, which Suchet still receives by the bucketload. And he answers every letter, something I know to be true from personal experience. My mum wrote to him in 1991, when he was playing the title role in Timon of Athens at the Young Vic; she told him about her two young daughters who adored him as Poirot and how she was bringing them to see him in the little-known Shakespeare play, even if most of it went over their heads. Suchet wrote back with the offer of tea and a chat before the performance. We sat in the Young Vic café, my sister and I, overwhelmed by our first brush with fame, while he coaxed conversation out of us and left us with the sense that the man who played our TV hero was every bit as kind and charismatic, chivalric and twinkly as the figure on screen.

Perhaps his special empathy comes from the fact that he like Poirot – a foreigner in England – has always felt himself to be an outsider. "Look at me!" he says now, pointing at his features. "I was always aware, especially with my colouring, I'm not the typical Brit." His paternal family was Russian Jews from modern-day Lithuania, chased by pogroms to South Africa; his father, John, trained as a doctor and arrived in Britain to become the unnamed lab technician who assisted Alexander Fleming with the discovery of penicillin. And in his later career, as a highly regarded Harley Street obstetrician, he delivered Anthony Horowitz, who would go on to write the Poirot scripts that cemented David's fame.

With his two older brothers, John and Peter, Suchet enjoyed a boarding-school education in which he excelled on the playing fields; he was a swarthy wing three-quarters, his thighs so large that he couldn't wear jeans, and he even competed in junior Wimbledon ("It was nothing as grand as it is today," he adds. "Don't let me show off!"). Choosing drama school over a medical degree did not meet with his father's approval – "he thought it very, very beneath him to have a son as an actor" – but his mother Joan was his ardent champion. Joan's mother had been a music hall artist and Joan herself was a hoofer desperate for a stage career. "It was rather tragic," explains Suchet. "She went for a small part in Antony and Cleopatra and she got turned down. And it broke her heart so much that she gave up."

Suchet's own theatre career belongs to the very top tier. His RSC roles have included playing Iago to Ben Kingsley's Othello; his performance in David Mamet's Oleanna, directed by Harold Pinter, secured the play's place in modern theatre lore; and anyone who saw him in last year's West End production of Long Day's Journey into Night will know just how intense and powerful a stage presence he is. It's a career he wouldn't have had without Poirot, he says – or without his wife, Sheila, who he fell in love with on sight in 1972, and who sacrificed her own acting career to help him pursue his and to look after their two children.

On the Poirot shoots, Sheila would be up at 4.30am to help him learn his lines; when he filmed the fiendishly difficult denouement scene on Murder on the Orient Express, she was sitting on set, in the adjacent carriage. "I must be the most difficult person that she has to live with," he smiles. "But we're still there! And we're very aware that time is running out, so we try and make the most of what we have together."

That will not include retirement any time soon. After completing a couple of documentaries, Suchet will tour Jonathan Church's production of The Last Confession to Canada, the US and Australia next year, and has a new play being written for him in 2015. Next Easter, meanwhile, will see the release of one of his most personal projects – an audiobook of the Bible, entire and unabridged, that he has been recording for the past two years, dashing into the studio whenever he wasn't shooting for TV or performing in the West End. (Being Suchet, it wasn't enough to merely turn up and read; he studied the context of every Old and New Testament book he read.) Suchet has been a Christian since reading a Gideon bible in a hotel room in 1986 and he hopes it will encourage people to encounter the Bible for the first time; after all, he chuckles, it's the only book that sells more than Agatha Christie, "but people read Agatha Christie!"

He has said he could be persuaded to return to his portrayal of Poirot if ever funding emerged for a big-screen version, but he won't be doing turns at home, he assures me. "Although one thing I've inherited from him is that when something surprising happens I will go: 'Oh la!'" And while he will miss the glorious, glamorous locations – Paris, Egypt, Tunisia – he won't miss the padding that was his constant companion in them. A cruise down the Nile, trapped in Poirot's body? He wags a finger in a distinctly Belgian way. "Impossible! Absolutely impossible!"

Suchet walks me to the door with all the chivalry of his departed friend. "I'm an old- fashioned man," he admits. "I think really I was born in the wrong century." As he says goodbye, he checks himself – "Delighted to have met you… again!" – and smiles, remembering the web. The Spider's Web. It sounds so much like an Agatha Christie mystery, I check it out when I get home. She wrote a stageplay, in 1954, with the title. I wonder if Suchet knows.

Curtain: Poirot's Last Case is on ITV on 13 November at 9pm. Poirot and Me by David Suchet is published by Headline, priced £20. To order a copy for £16, with free UK p&p, click here