Back in the early Nineties, Princess Diana — who'd recently separated from the Prince of Wales — came in and out of Vogue House all the time to borrow clothes.

One day, when we were short of one woman for a boardroom lunch at Vogue House, I thought we might invite her as a last-minute addition.

The occasion was a visit by Graydon Carter, the New York-based editor of Vanity Fair, who came to London regularly.

As the managing director of Conde Nast's British magazines —including Vogue, Tatler and GQ — I frequently put on lunches and parties for Graydon, then the toast of Hollywood with his annual Oscars parties.

My driver handed in a letter at the sentry box by the gate to Kensington Palace — and, within minutes, Diana was on the line saying she'd love to come.

The following day, a large photograph of her appeared on the front page of the Daily Mirror, showing her sunbathing topless on a balcony in Spain. It was rather blurred but it caused a scandal, and every columnist piled in.

Nicholas Coleridge (right) said that Cara Delevigne's (left) father told him that his daughter was 'tri-sexual'

The former managing director of Conde Nast's British magazines (Coleridge left) tells of an awkward conversation with Diana (right) about the size of her breasts

I thought: damn it, she's sure to cancel. The lunch was the next day. But her private secretary rang to say she was coming, though there could be no publicity, nothing. I must ring every guest and swear them to secrecy.

The princess arrived and looked fabulous. She sat between Graydon and me at lunch, and was very tactile. It was unexpected.

Diana touched your elbow, your arm, covered your hand with hers. It was alluring. And she was disarmingly confiding, speaking without filter.

'Nicholas, can I ask you something?' she said. 'Please be truthful. Did you see the photograph of me in the Daily Mirror? The topless one?'

'Um, Your Royal Highness, yes, we get all the newspapers in my office. I think I did glance at it . . . not that it was very clear.'

'William rang me from Eton. Poor boy, he's only 14. He was upset. He said some of the other boys were teasing him, saying my t*** are too small.'

She held on to my elbow. 'Nicholas, please be frank, I want to know your real view. Are my breasts too small, do you think?'

I became breathless, and went as red as a guardsman's tunic.

I stuttered: 'Er, Your Royal Highness, in as much as I can see under your suit, they seem, um, perfect to me. I wouldn't worry.'

'Thank you, Nicholas. I knew you'd tell me the truth. Thank you, I feel better now.'

At the end of the lunch, I walked her to her car, which was waiting outside Vogue House. Suddenly, four paparazzi sprang forward, taking a thousand snaps.

In the pictures, Diana looks radiant. I look like her bodyguard or stalker.

Afterwards, I rang a newspaper friend, to see if he could find out who'd leaked her visit. He rang back in five minutes.

'I just spoke to our picture desk,' he said. 'Diana rang herself from her car, on the way to lunch. She often tips them off about where she'll be.'

A few years before, I'd been editor of Harpers & Queen when Si Newhouse — the billionaire owner of Conde Nast in New York — offered me the job of editorial director of his British magazines.

Nicholas Coleridge says that he 'had a crush' on Samantha Cameron (pair pictured), the wife of former UK Prime Minister, David Cameron

Inside Vogue House, the magazines occupied one floor each. As you moved about the building, you felt the shifts in culture, almost all conforming to stereotype.

So Vogue really was populated by skinny fashionistas in black, with killer heels. House & Garden employed Tory matrons and pretty country girls; most had grown up in old rectories in Gloucestershire or Wiltshire. Tatler was staffed by party-minded, treacherous socialites.

From the outside, the Conde Nast of the late Eighties appeared as sleek and smooth as a well-oiled seal. From the inside, it was impossible not to notice the yawning chasm between perception and reality.

The publishers and advertising men were divided between those who went horse-racing midweek — the back seats of their Jaguars piled high with trilbies, race-cards and binoculars — and those who sat at their desks doing crosswords.

And the days of the managing director, Richard Hill — a tall, dashing figure, with military bearing — revolved around taking the company's biggest advertisers out to lunch. 'It's good news you've joined,' he said, affably. 'We're banking on you sorting out GQ — it's a bit of a shambles, apparently.'

'Anything in particular you see as a problem?'

He shrugged. 'God knows, I don't read it. I'm not one of those, you see.' He lowered his voice. 'Queers.'

I embarked on meeting the various editors, among them Robert Harling, the 81-year-old editor of House & Garden, who'd been a close friend of Ian Fleming and was said to be the model for James Bond.

Grace Jones (left) allegedly refused to perform at Fashion Rocks unless given more free clothes by Stella McCartney (right)

He wore skin-tight black leather trousers and a homburg hat, and lunched every day at the same table at Claridge's.

I made a remark about the smallness of the House & Garden editorial team, which then consisted of only 13 people (Vogue had 63).

'What if someone's ill?' I asked.

'Ill?' he boomed. 'Ill! Nobody on House & Garden is permitted to be ill. My young secretary came to see me last evening, saying she had a cold coming on, she might need to take today off. Imagine! She's only 20.

Cara Delevingne: 'I'm tri-sexual' Towards the end of my time with Conde Nast, my supermodel god-daughter Cara Delevingne became more famous daily. Without the slightest help from me, she started appearing regularly on Vogue front covers and gathered 40 million Instagram followers. An article in the Daily Mail splashed that Cara had taken a girlfriend, and I skimmed the news in the bath. Shortly afterwards, Cara's father, Charles Delevingne, rang. 'Seen the article today about your god-daughter?' 'I did spot it.' 'I just rang her. I asked: "Hey Cara, are you one?" 'She replied: "No, Dad, I'm trisexual. I try everything . . ."' Charles roared with laughter. Advertisement

'I told her: 'My dear, there's nothing in life which can't be solved by a good f*** or a gargle. That'll sort you out.' '

A couple of years later, Si Newhouse suddenly realised he had a blithering idiot in charge and sacked the managing director.

Not long afterwards, I was summoned to Paris for the day, to see Conde Nast's chairman, Jonathan Newhouse.

No sooner had I entered than he offered me the managing director job, while also remaining editorial director. He slid a sheaf of papers across the desk.

These, he explained, were the results of a handwriting analysis he'd commissioned from a French graphologist, based upon a letter I had written.

'I should clarify,' said Jonathan, 'we haven't made our decision to offer you the job based only on your handwriting. But these things can be perceptive.'

I took the role, and held on tight for the next 26 years.

Robert Harling finally retired from House & Garden, aged 84.

It was striking, when interviewing possible new editors, how many wanted to change the magazine into a version of hard-nosed, urban Elle Decoration.

I devised a killer question: 'Where do you stand on padded headboards?' Elle Deco people despised them.

They replied: 'They're seriously uncool. I like headboards on beds made of African Izombe wood or beaten corrugated metal.'

True House & Garden people replied: 'I adore padded headboards. You want them made quite high, so you can lean against them, covered with fabric.'

Cheryl Cole (left) is 'tiny' and bad at small talk and Kim Kardashian (right) 'talked about how much in love she was with her fiance; the marriage lasted two months', writes Nicholas Coleridge

The woman I appointed, Sue Crewe, passed the headboard test with flying colours.

In 2000, I became chair of the British Fashion Council. Each November, we staged the British Fashion Awards, which included dinner for 800-1,000 people, with every fashion house taking a table and boasting a pick'n'mix of celebrities.

Victoria Beckham made it a condition she'd attend only if her whole family was invited along, too — parents Tony and Jackie Adams, sister Louise, Louise's partner and more. It was my role to chat them all up at dinner.

The extended Beckham and Adams family was intriguing; their lives revolved around the fame of son-in-law David and eldest daughter Posh.

Jackie Adams told me that, every weekend, the family assembled at Victoria and David's country house ('Beckingham Palace') in Hertfordshire for lunch.

But it was ruined each time by journalists turning up and shouting questions through an intercom at the front gates.

Philip Green plays the dining room and relishes attention when he splashes the cash, according to Coleridge

'Have you considered switching off the intercom?'

'We can't,' wailed Jackie. 'What if an invited guest turned up and wanted letting in?' She complained their family holidays were regularly ruined by snooping reporters.

'Have you considered buying a holiday house with a very long drive?' I suggested. 'Do what the royals do at Balmoral and Sandringham. They don't get much disturbance, miles from anywhere.'

'It's OK for them,' said Jackie. 'It's not the same at all. David and Victoria are globally recognised.'

The Prince of Wales attended the British Fashion Awards as guest of honour and was a big hit. My job was to escort him down a line of designers, though the cast of characters was a minefield.

Alexander McQueen had once sewn the words 'I am a c***' into HRH's suit lining, while working at a Savile Row tailor; Stella McCartney was famously anti-foxhunting. Others might easily be drunk or coked-up.

The awards were the first time I'd witnessed the Prince of Wales in action. I noticed his neat way of disengaging from a group.

He makes a final point, laughs, shrugs, looks regretful, allows himself to be moved on, but then, as he walks off, turns back towards the group he's left, and laughs again, sometimes pointing his finger in a jocular manner, as if to say: 'You!'

The impression is that he's still engaged by the previous conversation. It provides elegant closure.

As he left the Fashion Awards at midnight, the prince turned to me. 'Perhaps you can dream up something to raise funds for my Prince's Trust, some kind of performance?'

Why Geldof the Tory despaired of book lover Hague One weekend, my wife Georgia, the children and I were staying in Sussex with friends. Also invited were William and Ffion Hague — William was Leader of the Opposition — and the Irish rock star Bob Geldof with his girlfriend Jeanne Marine and daughter Peaches. We were up and about at 6.30 one morning, having breakfast in the kitchen with the Geldofs. Across a stable yard was the Hagues' bedroom. The curtains remained defiantly drawn. Geldof, who turned out to be a Tory voter, gazed across the yard. 'I hope to f*** he's f***ing her,' he declared. 'If they don't produce a sprog before the General Election, we're f***ing finished mate, it's f***ing essential.' We ate breakfast. Hours passed. At last the curtains opened, followed by the door. 'Look out for high colour, the f***ing flush,' said Geldof. William and Ffion were wearing matching baseball caps. And he was carrying a hardback biography of Lord Salisbury. 'Morning all,' he said in his broad Yorkshire voice. 'Sorry we're late — I've been reading this fascinating life of the third Marquess of Salisbury.' 'We've only f***ing lost,' groaned Geldof. Advertisement

The idea we came up with was Fashion Rocks: 17 world-famous rock stars would perform one track each, while 17 international fashion brands put on catwalk shows simultaneously. We'd hire the Albert Hall, sell tickets and raise a million pounds.

Dior, Chanel, Gucci, Dolce & Gabbana, Armani, Yves Saint Laurent, Prada and Versace were approached, but none would commit until (a) all the others had already done so, (b) their rock act was better than the others, and (c) they'd been given the best models.

The rock stars were worse.

Robbie Williams was in, then out, then in again. Bryan Ferry said yes, but YSL's Tom Ford forgot to thank him, so he was nearly out again in a huff. Duran Duran were in, out, in.

There were bouts of model envy, rock-star envy, dressing-room envy, running-order envy, billing envy.

With a week to go, new problems emerged. Sheryl Crow had been signed to perform during the Ralph Lauren segment, but she'd run into Tommy Hilfiger at a party and now wanted to switch. Ralph Lauren went ballistic.

'If we don't get Sheryl, we're out,' said the Lauren people. 'And we'll cancel all Ralph Lauren advertising in Conde Nast magazines . . . worldwide.'

Fortunately, Ralph Lauren agreed to have the tenor Andrea Bocelli as their act instead — and then the dreaded evening arrived.

As the first guests were coming in, Grace Jones was holed up at the Dorchester, allegedly refusing to perform unless given more free clothes by Stella McCartney.

In the royal box, the Prince of Wales inserted cotton wool ear plugs from a monogrammed silver box. He removed them only once, for Andrea Bocelli.

As we continued to launch new magazines, it was a rare night that I didn't go to four or five events and parties.

Sometimes, my role was to entertain a cosmetics advertiser on one side at dinner, and a celebrity on the other. I kept notes on whom I found most and least alluring.

Heidi Klum (unexpectedly amusing); Elle Macpherson (a bit flaky); Samantha Cameron (slight crush on her); Kim Kardashian (talked about how much in love she was with her fiance; the marriage lasted two months); Cheryl Cole (tiny, not much small talk); Lara Stone (definitely sexy); Pippa Middleton (gorgeous); Jeremy Corbyn (we discussed Pink Floyd and the Corbyns' recent summer holiday at a Premier Inn hotel in Dundee).

With Philip Green, you felt he was playing to the room, relishing the attention. At a GQ dinner, he took a sip of wine and grimaced. 'Are you trying to f***ing poison me? I don't mean to offend, but I can't drink this.'

The claret, in all likelihood, was five up from the bottom of the restaurant's wine list.

'Ere, let me order some better wine,' he would continue. 'Don't worry, I'm paying, it won't be you.'

Then he'd order a bottle of claret ('No, make that three bottles') of vintages priced at £2,700 or £3,000. The bottles would arrive, cold from the wine cellar. 'That's better, isn't it?' he'd declare, beaming. 'That's more like it.'

Towards the end of my time with Conde Nast, I became chairman of the British group for a few years.

The perpetual low-level anxieties which had coloured my days, and which I'd worked so hard to conceal, fell away. I no longer worried incessantly about circulation, profitability or margins.

I felt like someone who'd swum a thousand miles through raging seas and reached, at last, a calm lagoon, and crawled up onto warm white sands.

The Glossy Years by Nicholas Coleridge will be published on September 26 by Penguin, £25. ©Nicholas Coleridge 2019. To buy a copy for £20 (20 per cent discount) go to mailbookshop.co.uk or call 01603 648155, p&p is free. Offer valid until 28/09/2019. Nicholas Coleridge will be appearing at the Henley Literary Festival on Sunday, October 6, at 2pm, interviewed by You magazine editor Jo Elvin. To book tickets, go to henleyliteraryfestival.co.uk or call 01491 575 948.