When Agatha Christie's moustachioed Belgian detective Hercule Poirot bade a final farewell to his legions of aficionados almost four decades ago, such was the shocking nature of his demise that he became the first fictional character to receive an obituary on the front page of the New York Times.

"Hercule Poirot Is Dead," mourned the headline on August 6, 1975.

Last year saw British fans grieve for Poirot all over again as David Suchet, who played the leading man in the ITV series, bowed out after 25 years when the television adaptation reached its inevitable conclusion in November. Yet, in a move that has both delighted and horrified connoisseurs, Christie's beloved literary creation, renowned for his dapper attire and curious clutch of eccentricities, has been resurrected in a new book.

As Poirot himself might say of the prospect: "Incroyable." But his return comes with the full blessing of the Agatha Christie Limited estate, including the late author's grandson Mathew Prichard, who has described the set of circumstances that led to commissioning the project as "pure serendipity".

Filling the lofty shoes of Christie most certainly isn't for the lily-livered. Still viewed by many as the queen of crime fiction, she holds the record as the most widely published author of all time - outsold only by the Bible and Shakespeare. With 80 novels and short story collections, 19 plays and a further six titles written under the name Mary Westmacott, Christie's books have sold more than one billion copies in English with another billion in foreign languages.

The woman tasked with breathing fresh life into the world's most famous detective is Sophie Hannah, who in recent years has carved a niche writing contemporary psychological thrillers, including The Telling Error and A Room Swept White. Her Poirot offering, The Monogram Murders, comes 38 years after Christie's last book, Sleeping Murder, was published and 39 years after the final Poirot novel, Curtain.

In the airy sitting room of her Victorian townhouse in Cambridge, Hannah, 43, is recounting how her remarkable role in the Poirot story came about. She's sitting on a blue velvet sofa, the walls behind her covered in eye-catching art. A trophy for the 2013 National Book Awards Crime Thriller of the Year - won for her novel The Carrier - is proudly displayed on the nearby mantel.

A self-described "obsessive Agatha Christie fan", Hannah admits that when her agent first said he had suggested her for the project, her immediate reaction was: "Oh no, how embarrassing - you didn't, did you?" Her dark curls bounce animatedly as she cringes at the memory. "I felt a bit like my mum had rung up the school and asked for me to be made head girl," she says.

As it transpired, it would be a neat twist of fate that put her name in the frame. Her agent was having lunch with an editor from HarperCollins and mentioned in passing he had an author who would be perfect at reprising the magic of Christie. As it happened, said editor was meeting with members of the Agatha Christie Ltd estate the following day. The idea of publishing a brand new book was mooted.

The next thing Hannah knew she was being wheeled out to pitch to a roomful of expectant ears. "I immediately thought of a particular idea for a plot and solution to a mystery I'd had," she says. "I'd tried for years to make it work in one of my contemporary thrillers but I just couldn't lever it in there. I kept shelving it and thinking I would use it later. What I had always liked about this idea is that it felt very Agatha Christie-esque.

"At my first meeting with the family I said: 'I feel quite cheeky even being here and suggesting it, but if you did want me to, here's a plot idea I might use.' They really liked it and agreed it was quite Agatha-ish, so everyone decided to go ahead. Mathew [Prichard] has since told me what made him most excited is when he saw what a massive fan I am of Agatha."

Having written Curtain: Poirot's Last Case in the 1940s, Christie cannily kept it under wraps until she was ready for it to be published some 30 years later. She passed away less than six months later on January 12, 1976. "I'm not the first person since Agatha's death to publish a Poirot novel but I am the first person to write a whole new story featuring Poirot," says Hannah. "A chap called Charles Osborne adapted Agatha's play, Black Coffee, which featured Poirot, and turned it into a novel. Mine, however, is completely new and original."

While the reaction from Christie's die-hard following has been for the most part favourable, Hannah concedes there is a minority outraged by the notion. "I'm getting hundreds of emails from Agatha fans all over the world," she says. "They write to me from England, America, China, Brazil, Mexico - I had an email yesterday from a Benedictine monk in Chile saying how excited he was about the new Poirot novel. That is really lovely and I would say the reaction I've had has been 95 per cent excited and positive with five per cent saying: 'Down with this sort of thing.'

"One woman said on Twitter recently: 'I hope Agatha curses this project from the grave.' Whenever anyone contacts me with that kind of comment, I always engage with them and say: 'I quite understand why people are nervous about this.' Everyone feels very proprietorial about Poirot, but I do try to reassure them that I'm approaching this not as a writer who wants a new gig, but as a passionate Poirot fan. All of the things they're worried about, I'm worried about too.

"The Poirot I've written about is absolutely in every detail Agatha Christie's Poirot," she adds. "The originality and innovation comes in with the story. My way of making it new is to bring an exciting and intriguing case to Poirot for him to solve."

Hannah's love for Christie's work began as a teenager when she devoured the entire back catalogue, including Murder On The Orient Express, Death On The Nile and Peril At End House, in less than two years. "My father, whose hobby was collecting secondhand cricket books, came back from a book fair one day with a copy of The Body In The Library," she smiles. "I don't know why he thought to buy it for me; I think he knew I liked mystery stories. I read it and absolutely loved it. I said: 'Right, Dad, from now on, every book fair you go to, any book by Agatha Christie - buy it for me.' Within about two years I had a collection of all of them and had read every single one. I can still picture my childhood bedroom in Manchester with all of these books."

Since being commissioned to write The Monogram Murders, Hannah has run the gamut of emotions from unadulterated joy to nervous trepidation. "I'm thrilled but obviously it is a daunting prospect because it felt like a very important task to be undertaking," she says. "With my other books, the only reputation at stake is my own. I was very conscious of making sure I did Agatha proud and didn't let her down."

Certainly, there is no question of Poirot coming back from the dead. Rather, the book sees readers comfortably whisked back to the 1920s where a retired Poirot has his quiet supper in a London coffee shop interrupted by a distressed young woman who claims her own death is imminent.

After she disappears into the night, a trio of murders in a hotel frequented by the fashionable, well-heeled crowd are revealed, each victim found with a monogrammed cufflink in their mouth. Poirot's famed "little grey cells" quickly fire into action as he offers to lend his expertise to Scotland Yard and rookie Inspector Edward Catchpool.

It is a far cry from the heart-rending spectacle of the frail and ageing Poirot depicted in Curtain. He is younger and sprightly, the trademark twinkle once again present in his eye. There is much to entice the razor-sharp reader, Hannah's narrative is peppered with cryptic twists, tantalising red herrings and an homage to one of Christie's most iconic plot devices - a body found in a room locked from the inside.

Capturing the essence of Poirot, insists Hannah, was "no difficulty at all" given that she knew Christie's body of work so intimately. "It was all already there," she says. "This was the best kind of assignment where you have done all of the research already. I have read the Poirot novels several times each and I just know him. Without thinking about what I know about him or how I know him, I know him in the same way that I know my husband and kids. If I had to write a book featuring them I would be able to write about them and it's the same with Poirot.

"In terms of getting into Agatha's head, having read all of her books more than once and having been so influenced by her, I just instinctively know what kind of story would appeal to her and what her priorities were in storytelling. You can tell that by reading all of a writer's work."

The biggest challenge, she concedes, was "knowing the other books featuring that character were written by the greatest crime novelist who ever lived". So no pressure, then? Hannah's brow momentarily furrows. "Agatha Christie's writing is incredibly skilful because her books are incredibly intellectually puzzling and challenging," she says. "If you want to test your wits, her books are perfect, but at the same time they are not difficult to read. You can let them wash over you, then be impressed at the end when Poirot reveals the solution.

"She really hits the nail on the head in terms of achieving the perfect meeting point of easy and difficult. That was the part I wasn't sure I would be able to do. My other books are challenging if you want to solve the mystery in the way that Agatha's are, but they are not the kind you can let wash over you. They make people feel as though they need to pay attention and that's deliberate because they are the kind of books I would want to read.

"Most crime fiction plots are not ambitious enough for me. I want something really labyrinthine with clues and puzzles, that will reward careful attention. My non-Poirot novels, they are not easy reads compared with some typical commercial thrillers."

One of the key elements of Poirot's enduring popularity, believes Hannah, is that he possesses the "perfect combination" of caricature and real character. "You sense that behind his words of wisdom, cleverness and compassion, there is a full, rounded and experienced man who has had a long and interesting life," she says. "He feels real and substantial but at the same time, on a superficial level, he is as vivid as any caricature with his egg-shaped head, green eyes and moustaches. That is very rare. Most characters in fiction are either caricature or real three-dimensional characters, but Poirot manages to be both."

The eldest of two daughters, Hannah grew up in Manchester. Her father Norman was a university lecturer and Marxist academic while her mother Adele wrote children's books. Hannah published her first volume of poetry, The Hero And the Girl Next Door, aged 24 and soon afterwards was offered the role of fellow commoner in creative arts at Trinity College, Cambridge, a post she held between 1997 and 1999.

"Basically it means writer-in-residence and that was what changed my life," she says. "I was working as a secretary in Manchester and thought I would always do that. Then I got this letter offering me a two-year fellowship where I could write, they would pay me a salary and give me a flat to live in. It was heaven. I felt like little orphan Annie arriving at Oliver Warbucks' house.

"Before that I lived on a street in Manchester where you wouldn't open your door if someone rang the bell. At that time there was a spate of robberies where people would just ring doorbells and walk in with a gun. We lived near Moss Side. I had been held up at gunpoint, as had my husband. It was quite rough. I took it in my stride because I thought that was just what life was like. Then suddenly, there I was living in beautiful Trinity College, Cambridge, where nobody held me up at gunpoint and instead gave me nice sherry and cheese. I thought: 'This is more like it.'"

While she and her husband Dan, 45, an artist and writer, later spent a decade living in Yorkshire, they returned to Cambridge in 2010 where they live with their children, Phoebe, 11, and Guy, 10, and a Welsh terrier called Brewster. Hannah lists her hobbies as "swimming, walking and dog fanatic" alongside "anything to do with mysteries, detective novels and crime dramas".

She admits to being left cold, however, by the Scandi-chic television series which have been popular in recent years, preferring American shows such as Breaking Bad, The Shield, House ("even though that's not crime, it's medical mystery"), The Good Wife, Sons Of Anarchy and Dexter.

"I watched the first series of The Killing and was so disappointed it slightly put me off," she says. "I quite wanted to know who had murdered Nanna Birk Larsen, but the way the plot was wrapped up was so shoddy and full of holes I really got cross. I thought: 'I've watched this for 20 hours and this is the best they can do?' It's not hard. One editorial meeting could have sorted out all of those plot holes."

In literary terms, Hannah views longevity as a more accurate barometer of success than selling millions of copies or topping the book charts. "I would love to be someone like Agatha Christie, Ngaio Marsh, Ruth Rendell or PD James; authors who get to age of 90 and suddenly you find they have written 400 books," she says. "To be able to keep writing books into old age would be lovely."

The Monogram Murders by Sophie Hannah is published by HarperCollins, priced £18.99. The Telling Error is out in paperback, published by Hodder & Stoughton, priced £7.99. Hannah will be at the Bloody Scotland crime writing festival in Stirling on September 21. Visit www.bloodyscotland.com.


The Monogram Murders by Sophie Hannah marks the latest in a growing line of what has been dubbed the "continuation novel", designed to help new readers fall in love with bygone writers and, cynics might say, keep the money rolling in for their publishers.

HarperCollins also coined the idea for The Austen Project: six classic novels by Jane Austen rewritten for a modern audience. The collection began with Sense And Sensibility by Joanna Trollope, pictured, with the second instalment, Val McDermid's reworking of Northanger Abbey, published earlier this year. Curtis Sittenfeld's Pride And Prejudice and Emma by Alexander McCall Smith are currently in the pipeline.

Other authors have also followed in this vein. Sebastian Faulks turned his hand to Ian Fleming's James Bond with Devil May Care in 2008 and PG Wodehouse's much-loved characters Jeeves and Wooster last year. Jeffery Deaver and William Boyd have also written Bond novels, while Anthony Horowitz penned a Sherlock Holmes book, The House Of Silk, in 2011, and has a sequel, Moriarty, due out next month.