Susannah Constantine is best known as one half of Trinny and Susannah – the posh pair who told people how not to dress in the 2000s.

Since then Susannah, now 60, has been Anton Du Beke’s worst ever partner on Strictly Come Dancing and the first to be voted out of the jungle when she appeared (briefly) on I’m a Celebrity.

But had her history gone a little differently she might have been a member of the royal family.

On Thursday she will be in Norfolk to talk about her astonishing, frank and frankly hilarious, memoir Ready for Absolutely Nothing.

Far from telling people how to dress to conceal insecurities (famously Susannah and Trinny majored on ‘tits, bums and saddlebags’) the book reveals her own insecurities - and takes readers on an exuberant romp through a back-story packed with wealth, royalty and international celebs.

Her television years turn out to be perhaps the least interesting part of her life.

“These are stories that I never really discussed with anyone. Elton John was just gobsmacked and said he couldn’t believe this was my life!” said Susannah, who dated Princess Margaret’s son, David Armstrong-Jones, in her 20s.

“I think the thing people have been most surprised about is that all the anecdotes about the royal family, and rock royalty, have never surfaced before.

“Everything is written with a huge amount of love and respect. Princess Margaret was like a surrogate mother to me, and the Queen Mother like a surrogate grandmother. David got a copy of the book before it went to press and was thrilled because it is like a love letter to his mother.”

One fabulous anecdote involves the late Queen and Margaret Thatcher tussling over a teapot.

“The Queen asked me if I would like a cup of tea and picked up this huge Brown Betty teapot. I handed my cup and saucer over for her to fill and these hands shot by in front of me and it was Margaret Thatcher!” said Susannah. “She tried to take the teapot out of the Queen’s hands and the Queen did not like that so she pulled back, and Margaret Thatcher tried again and she pulled back again.

“It was extraordinary to see the two most powerful women in the world tussling over a teapot.”

It would have made a wonderful scene in The Crown, which Susannah loves – and has a better insight than most into where fact morphs into fiction.

Even after Susannah and David split up, and she was about to marry her husband of more than 25 years, with whom she has three grown-up children, Princess Margaret hosted her engagement dinner.

Susannah’s actual family were rich too but her mother had severe bipolar disorder and there were suicide attempts and alcohol addiction.

In 2020 Susannah revealed she battled alcoholism herself and it was the process of looking back to try to find out why she had become addicted which inspired Ready For Absolutely Nothing.

But there is nothing of the misery memoir here. Jaw-dropping revelations range from the childhood nanny who was also working as a prostitute to her life as an almost-royal.

“As someone who never looks back, I began remembering all these incredible times, the amazing people that I met, witnessing all these fascinating moments in social history,” said Susannah. “It was like I was writing about a character because I hadn’t thought about all these things.

“My parents only had one ambition for me and that was to get married. When I suggested university, and God knows how I’d have got in with my terrible schooling, my father said, ‘Don’t be silly you’ll be better off learning how to make a good beef Wellington.’

“But when he died I found cuttings of every single thing I had written.

“I have always worked. That was my rebellion. It wasn’t sex, drugs and rock’n’roll. It was always, ‘I’m not going to marry some chinless wonder and I’m not going to end up like my mother. I’m going to go out and work and earn some money.’”

Between royalty and marriage she dated cricketer and future prime minister of Pakistan Imran Khan, and developed a love of cricket herself which led, via meeting the sports editor of the Daily Telegraph, to reporting on women’s cricket – and then a weekly fashion column for the newspaper. With co-writer Trinny Woodhall, who now runs a makeup business, Ready to Wear focused on high-street fashion, illustrated with photographs of the pair modelling the clothes.

“It was fashion done in a very different way,” said Susannah. “It was looking at how emotive clothes can be and the positive psychological impact they can have when you look good.”

The format moved to television and What Not to Wear ran on the BBC from 2001 to 2005. There were regular makeover slots on Richard and Judy and Oprah and a clothing range for the Littlewoods catalogue. A fashion booklet they wrote caused much hilarity when pictures turned up on social media a few years ago, advising women that a dress over jeans made a great interview outfit.

Susannah stayed in the public eye with appearances on both Strictly Come Dancing and I’m A Celebrity...Get Me Out of Here.

“Both of which I came last in, let’s not forget!” she laughed.

“When I went into Strictly I had never watched it. I lied and said I had and that was my first massive mistake. But I’d had this recurring dream about being a brilliant dancer so I went in thinking I could dance.

“Anton said later that as soon as I walked through the door he knew there was no hope. But he was so wonderful and encouraging and inspiring that after day two of rehearsals I came back home and said I thought I’d found something I was really good at.

“Two days later I came back said I thought we could win. Wind the movie forward and you see me on our first dance where I looked like Eva Peron about seven years into the tour of her corpse. Complete rigor mortis. Then I wanted to do a showy end – and looked like a sack of potatoes being lobbed across a barn floor. It was without question the most humiliating and terrifying experience of my life.”

Her memoir, published this month, has already been considerably more successful. The royal chapters bring in some of the same characters as Lady Ann Glenconner’s wildly successful biography Lady in Waiting: My Extraordinary Life in the Shadow of the Crown.

Susannah knew the aristocratic Norfolk nonagenarian and sent her an early draft.

“I got a call a day after it arrived and she said, ‘Susannah, it’s Ann Glenconner, I’m furious with you.’ And I thought, ‘Oh no, I’m going to have to rewrite huge chunks.’ And she said she had started it at 5pm and stayed awake until 3am reading, and it was absolutely wonderful!”

When Susannah comes to Norfolk (and she is a regular visitor) she hopes to drop in on Lady Ann.

Writing the book means there has been a break in her 2020-launched podcast, My Wardrobe Malfunction, with its starry line-up of guests. Her own worst wardrobe malfunction was a typically hilarious combination of top royals, a glittering social occasion, and terrible embarrassment.

“I was at Windsor Castle having dinner, wearing this beautiful Valentino dress that my dad had bought me (so spoilt!) and I was sitting next to Prince Philip,” she said. “We were eating our first course and I felt him move his hands over to my chest and I thought, ‘Oy oy what’s going on here?’ But he was holding up the front of my dress because my boobs were on total display. The straps were broken and he got a footman to get some safety pins and rescued me!”

Susannah’s wardrobe staples now are jeans and wide-legged trousers and she said: “It’s very hard for me to find clothes because they are either very tight and I'm too old for that, or they’re very androgynous and my boobs are too big to look good in those.

“I love looking nice and I haven’t given up, but I’ve definitely become the kind of woman who needs Trinny and Susannah!

Susannah Constantine will be at Jarrold, Norwich, to talk about Ready for Absolutely Nothing at 6.30pm on Thursday October 27. Tickets from Jarrold.