Fergie flies out for her party date with Kate

Now, despite a 15-year age gap, the Duchess of York and the queen of cocaine, Kate Moss, will be ringing in the New Year together - and have taken their three children along for the ride.

The fact that the former royal has chosen to allow the Queen's granddaughters Princess Beatrice, 18, and 16-year-old Princess Eugenie, to spend the New Year celebrations with notorious party animal Miss Moss is bound to raise eyebrows at Buckingham Palace.

And it follows an earlier gaffe earlier this summer when she took her youngest daughter - who has just started studying for her A levels - to a lavish 'Eurotrash' bash thrown by rapper P Diddy on his yacht in St Tropez.

The Duchess of York and Miss Moss - whose career has gone from strength to strength despite being exposed as a heavy cocaine user last year - are both renting luxury villas at the exclusive Amanpuri resort on the island of Phuket.

They are to be guests of honour at a lavish New Year's Eve party held a little further down the coast by multimillionaire socialite David Tang.

The 47-year-old Duchess, seen here jetting out of Heathrow on Wednesday afternoon, is holidaying with her two children, who are fifth and sixth-in-line-to-the-throne.

Looking colour-cordinated in black and white outfits with almost identical flat pumps, the trio laughed and smiled as they checked in their baggage before hopping on a Malaysian Airways flight to Bangkok.

Just an hour or so after the royal party departed, supermodel Miss Moss, 32, arrived at the airport with her five-year-old daughter, Lila Grace, and a handful of friends - although there was no sign of her heroin junkie boyfriend, Babyshambles singer Pete Doherty - to catch a later British Airways service.

After a short connecting flight at the other end, both groups arrived at their luxurious £5,000-a-week Thai-style private villas, each of which has its own plunge pool, open air living room known as a 'sala', and live-in maid and cook.

Amanpuri, which means 'place of peace', is one of the most exclusive resorts in the world, meaning the Duchess and Miss Moss will be able to laze around its black-tiled swimming pool far from the inquisitive glare of the paparazzi.

The Duchess first met Miss Moss at Mr Tang's 50th birthday party in Bhutan two years ago and was later that year seen with the model at party at the Sketch club.

Photographs showed the Queen's former daughter-in-law looking tired and slightly worse for the wear with the model hugging her enthusiastically Friends acknowledge that the Duchess and Miss Moss are likely to spend time together at the bash.

"The Duchess has been invited out to Thailand by her great friend David Tang and his wife Lucy and decided to take the girls with her as her ex-husband, Prince Andrew, had them with him at Sandringham for Christmas. David has two children himself, who the girls know well, so it will be a real family occasion," said one.

The friend continued: "The Tangs, who are incredibly generous hosts, are also holding a New Year's Eve party to which he has invited several other friends who are holidaying in the area, including Kate Moss.

"By coincidence she and the Duchess are staying at the same resort, which is something of a mecca for luxury holidaymakers at this time of year.

"She and the Duchess have met at several of his parties before and are on friendly terms but they are certainly not holidaying together.

"The trip is about Sarah and the girls having a fabulous holiday and spending some quality time together."