Diana, Princess of Wales, died when the car carrying her and her lover Dodi Fayed crashed at high speed in Paris, trying to outrun a group of press photographers in a tunnel near the Seine. Dodi and Henri Paul, the car's driver, were killed instantly, while Diana was pronounced dead three and a half hours later, at 4am on August 31, 1997.
Later that same day, Tony Blair addressed Britain from his constituency in Sedgefield, where he paid tribute to the "people's princess". It was a phrase coined by Alastair Campbell, the prime minister's press secretary: the work of a moment, but it defined her in death in a role she had never truly held in life. And in the extravagant grief it implicitly sanctioned, it defined a nation and a moment in history.
By the time of Diana's funeral six days later, the flowers laid at the gates of Kensington Palace were stacked a metre and a half deep. Three million people congregated in central London to pay their respects; more lined the 70-mile route from there to Althorp, the Spencer family's Northamptonshire estate, where Diana was finally laid to rest.
Amid all this, one image resonated: that of Princes William and Harry walking behind their mother's funeral cortege, stoic in the face of a loss too profound to be freely expressed. As they did so, they were watched by 2.5 billion people around the world.
But what if one of that number was their mother? What if the fatal incident were nothing but a sham? What if Diana hadn't died? These are the questions posed by Monica Ali in Untold Story, her fourth novel.
As she began to work on this book, Ali says she found herself wondering "what if the accident had never happened, how would she have emerged from that period in which she seems to be at some kind of crossroads?"
Setting aside for one moment the question of taste that such a speculative fiction is bound to elicit, it's an interesting enough premise. Unfortunately it's one Ali jettisons almost immediately. She doesn't have her princess "emerging" from that period at all, she simply has her disappearing in a different fashion.
Ali's princess survives the Paris car crash and goes on to stage her own drowning some months later, slipping off the side of the yacht on which she and her lover are holidaying, before swimming to the sanctuary of her former private secretary, Lawrence Standing. He is a bit in love with Lydia, as Ali's princess is called, complicit in her "little plan" and bobbing in a boat nearby, waiting to paddle her to freedom ... whatever that is.
We meet this reimagined princess of Wales a decade after her public death. She is living as Lydia Snaresbrook and home is the Midwest of America and a small town called – wait for it – Kensington.
She has a select group of female friends neither probing enough to ask, nor sharp enough to wonder, about the past life of the woman in their midst. When she arrived it seems they were conveniently happy with evasive talk of a "cruel but powerful husband" and his "cold family". She has a boyfriend, Carson, who seems to have strayed from the pages of Mills & Boon. He is toned and handsome and, given that he is an insurance claims adjuster, remarkably willing to leave the investigative rigour of his workplace at the door when it comes to his partner's past.
Lydia's blonde hair has been dyed dark and the features of the woman who was once the most photographed in the world have been altered by cosmetic surgery - a nose job and a lip plump. She works at a neighbourhood dog shelter. She swims every day. She misses her sons. She has established a fragile peace that is threatened when "Grabber" Grabowski, a paparazzo who once hounded her, arrives in town.
The 10th anniversary of the "death" is approaching. Grabowski is in Kensington compiling a book of previously unseen pictures of Lydia, cashing in - a difficult punch for Ali to land, given the nature of her own fiction - when he spots her. Physical attraction turns to professional compulsion as he realises her eyes are identical to those of the princess.
As Untold Story progresses, it skips through genres like a pebble skimming water. Ali introduces it as a fairy tale then switches to schmaltzy romance. She teases the reader with the possibility of something more incisive, before settling finally (and most successfully) on thriller.
Structurally Ali returns to a technique she employed with greater effect in Brick Lane, creating our triumvirate of lead characters - Lydia, Lawrence and Grabber - through a mixture of third-person narrative, diary entries and letters. This opens up the possibility for insight into their inner lives, but perplexingly, when it comes to her princess, Ali holds back, as if uncertain where the fact of Diana ends and the fiction of Lydia begins.
It has been said that Ali courts controversy. Certainly her inspiration seems to be ever more obviously torn from the headlines of the day, and it can't hurt sales that this book's release collides with Prince William and Kate Middleton's wedding. Already there is talk of a film. Ali herself has observed: "When William put that ring on Kate's finger what that did, and he must have known, was to put Diana back in people's mind - front and centre."
Some may squirm at this timely resurrection of Diana, but then commercial fiction, and we are squarely in that territory here, is all about currency in every sense of the word. Besides, the problem with Untold Story is not that its author seems to be courting controversy; it's that, in every page, she seems to be backing away from it and so from the truth of her original inspiration and her central character.
Ali has insisted in interviews that "Lydia is not Diana", but she protests too much. Her background, her physique, her disastrous relationships all belong to Diana. Her desire to have been Queen of Hearts, her tortured recollection of watching her two boys walking behind her coffin would surely, in this parallel reality, be Diana's. And if Lydia is not Diana, or some speculative version of her, then who is she?
It's tempting to think that the author herself is unsure. Perhaps part of the problem is that the Diana of Ali's inspiration was, to some extent, a fiction herself; a public version of a private person who, for all the research to which Ali lays claim, remains unknown.
In one of his diary entries, Lawrence Standing reflects on his former mistress's paranoia and fame: "Press exposure and public scrutiny ... she had lived with it for such a long time, why not carry on indefinitely? Perhaps that question is built on the premise that one eventually becomes immune to these things. This is my only 'insider' knowledge: she never took it in her stride."
That this should be his only "insider knowledge", is absurd. But again and again Ali reaches the limits of her knowledge of Diana and stops. Time and again there are hints of the better book that this could be. Diana professed to fantasising about leading a "normal life". But she was complicit in her own celebrity; if stripped of it might she miss it? Would fear of discovery be mixed with some contradictory thrill? If really given the chance to live out this fairy tale reversal, could that narrative lead any more convincingly to a "happily ever after"?
"I changed everything, so I thought everything would change ... I always had someone to blame before," Lydia writes in one letter to Standing. "I've run out of culprits now."
Writing recently, Ali explained how, during a stint as a visiting professor at Columbia University, New York, one of her students asked how she chose her subjects and if, after her experiences with Brick Lane (the debut novel that saw Ali lauded and denounced in almost equal manner) she consciously steers away from subjects that might be controversial.
"I told them that I write with the door closed with no one looking over my shoulder," she said, "or else there would be no point in writing at all. That's certainly what I tried to do when I was working on my latest novel ... to be honest, in the early stages of thinking about the book, I didn't entirely manage to keep the door bolted. I was aware that some people might raise their eyebrows at the subject matter ... I knew that I might be judged not on the basis of the work, but of people's preconceptions of it."
It is an anxiety that Ali just cannot seem to shake. She is hamstrung by her inspiration. Ali is right in her assertion that this work should be judged on its merit as fiction. It is as a fiction that it falls short, in part because its author never truly moves beyond the "What if?" of the premise. Instead the question stays, nagging and close, as every coy reference to Diana's life only serves to make Lydia and her story, told or otherwise, less credible.
Laura Collins is a senior features writer at The National.