LONDON - Few men would feel comfortable hearing their future wife compared to their mother. But that is what Prince William would face week in, week out, had he the time and inclination to wade through the royal press cuttings.

Commentators have been quick to compare and contrast royal fiancee Kate Middleton with William's late mother Princess Diana, whose style, charity and scandalous divorce from Prince Charles made her arguably the world's most famous woman.

Yet the differences far outweigh the similarities, experts and PR gurus say, which could bode well for the young couple's long-term happiness as well as Middleton's relationship with the Queen and her royal brood.

"As a PR person, which is what I have been for 45 years, I would say Princess Diana was a one-off," said Max Clifford, one of Britain's most prominent image makers.

"She (Diana) became just about the biggest star in the world. She became far more popular all over the world than the royal family. I think Kate's going to be far more controlled, she's going to be far more part of William."

Diana was just 19 when she was betrothed to William's father Charles in 1981. He was a 32-year-old veteran and she a timid newcomer to the "goldfish bowl" life of a leading royal whose fashion sense was more "Sloane Ranger" than sophisticated chic.

But as her relationship with Charles and the royal family soured, her confidence, sense of style and stature as a charity figurehead grew, making her a favourite with the public.

NUN'S COMPASSION, SUPERMODEL LOOKS

Arthur Edwards, the Sun tabloid's veteran royal photographer, agreed that Middleton was more likely to see her role as a foil for William rather than a lone star.

"She (Diana) had this compassion of a nun but the looks of a supermodel. We've yet to see if Kate's going that way. I suspect maybe not, I think maybe she'll be more of a support to Prince William and less of an individual in her own right."

The royal family had learned from its mistakes, Clifford added, and William would be desperate to avoid exposing his wife to the kind of media circus his mother had to cope with by the time of her death.

Diana was killed in a Paris car crash in 1997 after being chased at high speeds by paparazzi photographers. She was 36.

"The royal family have moved on," he said. "They've had to, to the realities of the media world in 2011. She will be, I imagine, the devoted wife and very much at his side.

"Kate the individual I don't believe will receive a fraction of the coverage that Diana got worldwide and in many ways it's going to be a lot easier for her because the palace and all those around will have learned from what happened with Diana.

"They will be very, very guarded to make sure that doesn't happen again."

In contrast to Diana's perceived naivety at the time of her marriage, the 29-year-old Middleton is nearly 10 years older and has known William for a long time. They met at university a decade ago.

BACKGROUNDS LIKELY TO COUNT

Royal watchers also believe that Middleton's family is more stable than Diana's, whose parents split when she was a young girl. According to a BBC obituary, the children became "pawns in a bitter custody dispute".

Claudia Joseph, author of Middleton biography "Kate", said the contrast between the two women was stark.

"Diana hailed from an enormously privileged, aristocratic, old English family. Kate comes from a family that descends from working class mining stock. In many ways, she had a much more modern upbringing.

"Diana's parents were divorced, she was only 20 years old and a much more fragile and troubled character when she walked down the aisle of St Paul's," Joseph added.

"Kate comes from a much more stable background -- she is ... in every sense, more mature, well-grounded and comfortable in her own skin." The fact that William and Middleton are so close in age could also help them bond, Joseph said.

The couple should realise that the overwhelmingly positive press coverage they have enjoyed since announcing their engagement in November may not last, former newspaper editors have warned.

Signs of ongoing tensions between the monarchy and the media resurfaced this week when Middleton's mother and sister were photographed shopping together in London, prompting a warning to newspapers from Britain's Press Complaints Commission.

Royal commentators believe William, who gave Middleton Diana's old engagement ring, is trying to protect his fiancee from the problems his mother faced at the same time as preserving Diana's memory on the big day and afterwards.

"William has been quite shrewd to exploit the Diana connection," said royal biographer Christopher Wilson.

"The choice of the engagement ring was ... a defence mechanism -- 'keep away from my woman' sort of thing."