Her award-winning historical novels chronicle the brutal fate suffered by Royal consorts in Tudor times.

Now Hilary Mantel has delivered a withering assessment of Kate Middleton, dismissing the Duchess of Cambridge as a personality-free “shop window mannequin”, whose sole purpose is to deliver an heir to the throne.

The pregnant Duchess is a bland, “machine-made” Princess, “designed by committee” who lacks Anne Boleyn’s cleverness and Diana’s ability to transform herself into an avenging wraith, the double Booker Prize-winning writer claimed.

Delivering a London Review of Books lecture on Royal Bodies at the British Museum, the author of Wolf Hall and Bring Up The Bodies, the acclaimed novels which detail the failure of Henry VIII’s wives to produce an heir, examines the prospects for the future queen consort.

On first impressions, Mantel believed Kate Middleton to be “a jointed doll on which certain rags are hung. In those days she was a shop-window mannequin, with no personality of her own, entirely defined by what she wore.”

Prince William’s wife-to-be was as “painfully thin as anyone could wish, without quirks, without oddities, without the risk of the emergence of character."

“She appears precision-made, machine-made, so different from Diana whose human awkwardness and emotional incontinence showed in her every gesture.”

The Duchess of Cambridge “appeared to have been designed by a committee and built by craftsmen, with a perfect plastic smile and the spindles of her limbs hand-turned and gloss-varnished.”

Ms Mantel said: “Presumably Kate was designed to breed in some manners. She looks like a nicely brought up young lady, with ‘please’ and ‘thank you’ part of her vocabulary.” But in her first official portrait since marrying William, painted by Paul Emsley and unveiled last month, “her eyes are dead.”

Kate is quite unlike Anne Boleyn, who was “a power player, a clever and determined woman.” Although the Duchess will probably escape a beheading, their fates will be similar. “In the end she (Anne) was valued for her body parts, not her intellect or her soul; it was her womb that was central to her story… a royal lady is a royal vagina.”

Female Royals are “persons but they are supra-personal, carriers of a blood line: at the most basic, they are breeding stock, collections of organs.”

Whilst St James’s Palace fumes at pictures of the Duchess in a bikini showing a slight baby bump in a number of foreign magazines, taken during a break on the Caribbean island of Mustique, Mantel observes: “The royal body exists to be looked at.”

The author compared the Royals to pandas. “Our current royal family doesn’t have the difficulties in breeding that pandas do, but pandas and royal persons alike are expensive to conserve and ill-adapted to any modern environment.

“But aren’t they interesting? Aren’t they nice to look at? Some people find them endearing; some pity them for their precarious situation; everybody stares at them, and however airy the enclosure they inhabit, it’s still a cage.”

The death of Diana, who “passed through trials, through ordeals at the world’s hands…wasn’t just an accident,” Ms Mantel said. “It was fate showing her hand, fate with her twisted grin.”

Whilst Ms Mantel’s speech was “brilliantly written,” Ingrid Seward, editor-in-chief of Majesty magazine, said she was being unfair to the Duchess. “When Diana came on the scene she would just sit there and look pretty. We all thought she was pretty bland. It wasn’t until later that we learned about all the troubles of her marriage and her personality began to shine through. Kate might yet come into her own.”

The Royals’ glad-handing duties mean they “can’t do anything that might reveal their personality,” Ms Seward argued. “They have to be nice to everyone. They are probably stupefyingly bored but they can’t appear to be having anything other than a nice time.”

The Duchess chose today to give an insight into the causes that she will support, hailing the start of a project which will see one of her charities receive a huge financial boost from a philanthropic organisation.

She described her delight at Action On Addiction, which she backs as patron, becoming the beneficiary of the fundraising efforts of 100 Women in Hedge Funds during 2013.

"Those affected by addiction are in desperate need of the highest level of care and treatment; Action On Addiction delivers this brilliantly,” she wrote in a letter to mark the launch of the fundraising project. “Whether direct or indirect, the impact of addiction can be devastating.”

On Tuesday, she will visit the addiction charity's Hope House treatment centre, in Clapham, south London, to meet women recovering from alcohol and drug dependency.

Prize fight: the author and the princess

Hilary Mantel
Age: 60
Occupation: author
Education: studied law at LSE and Sheffield University, where she discovered socialism.
Experience: Social worker in geriatric ward; department store sales assistant. Has lived in Botswana and Saudi Arabia.
Literary credentials: author of more than a dozen books, including Wolf Hall and Bring Up The Bodies, the first two parts of a trilogy about Thomas Cromwell, both of which won the Man Booker Prize.
Style icon? Reflecting on her body image, she once wrote: “You throw tantrums in fat-lady shops, where the stock is grimy tat tacked together from cheap man-made fabric, choice of electric blue or cerise. You can’t get your legs into boots, or your feet into last year’s shoes.”

The Duchess of Cambridge
Age: 31
Occupation: princess.
Education: Marlborough and St Andrew’s, where she caught Prince William’s eye modelling lingerie.
Experience: Keeping world’s media at bay during nine-year “will-they, won’t they” relationship with William.
Previous employment includes stints at Jigsaw (as a buyer) and, in various part-time roles, working for her parents’ firm Party Pieces.
Literary credentials: sister of the author of Celebrate, a book about parties.
Style icon? The Duchess’s fashion style has been extravagantly praised by, among others, Tatler, the Daily Telegraph, People and Vanity Fair.