Still friends: Pippa Middleton and rumoured old flame George Percy on a minibreak in Madrid last month
Just at a time when her image couldn't be more impenetrable, Pippa Middleton has dared to divide opinion.
For when she departed with friends two weeks ago for a mini-break to Madrid, the group was accompanied by a young man by the name of George Percy, one of her former Edinburgh University flatmates.
But there's much more to the 'close friend' than meets the eye. For the aristocratic son of the Duke of Northumberland - whose home, Alnwick Castle, doubles as Hogwarts in the Harry Potter films - is also reported to be one of Pippa’s past flames.
So, along with issuing an edict on how to be a faultlessly eye-catching bridesmaid, Pippa is now also seemingly on her way to breaking one of life's greatest taboos. Is it suddenly acceptable to holiday with one’s ex?
Of course, she is hardly the first to test these waters. Looking back over the various chequered histories of broken relationships, the celebrity world is alive with examples of people who elect to spend their free time with previous partners.
Actor Jude Law and his former wife Sadie Frost have always sought to quash rumours that their current friendship, which followed a six year marriage, is one full of strain. They happily prove that life is anything but acrimonious by frequently being photographed on holiday together with their three children – and Sadie’s son from another marriage.
In fact, it was only this Easter that Jude's wide-smiling brood joyfully posed for photographs at a showing of the Blue Man Group in Las Vegas, just as two years ago, they wore the very same gleeful faces on Brazilian beaches where they soaked up some winter sun.

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No obvious hair-tearing in this post-marriage holiday match.
Other repeat ‘ex offenders’ are Hollywood stars Bruce Willis and Demi Moore, whose free-flowing compliments of one another have helped depict divorce as anything but discordant.
Customary as it is to see these two happily arriving together – along with their respective new, and much younger, spouses – at parties and film premieres, that one does wonder what it was that caused their separation eleven years ago in the first place.

Happy families: Jude Law and ex-wife Sadie Frost in Vegas with a cast member from the Blue Man Group and their children Rafferty, Iris and Rudy

The Duke and Duchess of York, who divorced not long after Sarah Ferguson was snapped having her toes improperly sucked by a man who was not Prince Andrew in 1992, have claimed in the past to being 'the happiest unmarried couple' in the world.
And they’re not afraid to show it, either. For not only have the pair – who are parents to Princesses Beatrice and Eugenie - enjoyed frequent meals a deux in Mayfair, London’s exclusive dining quarter, but in August 2009, departed for a secluded Spanish mountain villa for a fortnight in order to enjoy some ‘relaxing bliss’ alone.
'He’s a fantastic father and friend, and you cannot put Andrew and I in a box of any description,’ flame-haired Fergie revealed.
So what is their secret? And what is it that binds estranged couples together long after the rows and altercations, which cracked them from the start, have subsided?
‘In most cases, children are the reason warring partners strive to find the energy to remain on good terms,’ says one relationship expert.

Compliments: Bruce Willis in 2008 with now wife Emma Hemming (left), daughter Tallulah Belle Willis and her mother and his ex-wife Demi Moore

Hitting the slopes: Sarah Ferguson, left, Prince Andrew and daughter Beatrice, right, ski together in the exclusive resort of Verbier

'Sometimes it’s strained, other times it’s not, but offspring often serve as a bond eternally tying people together, whether they’re still intimate, or not.'
In Vacationing With My Ex, Arianna Huffington – founder and editor-in-chief of The Huffington Post - blogged movingly last year while on her first holiday with the husband she had divorced twelve years earlier.
‘This kind of concentrated together time can often prove to be stressful,’ wrote the mother-of-two. ‘But we are having a fabulous time, hanging out as a foursome, eating breakfast, lunch, and dinner together, and exploring the exquisite beauty of Crete.

Surviving as friends: Arianna Huffington went on holiday with the man she had divorced 12 years earlier
‘It's been especially great for the kids to have their parents not only not be on edge with each other, but actually enjoying one another's company. While we did not survive as a couple, at least we've survived in the joint parenting of our daughters.’
Spending time with someone whom one knows, let’s say, inside and out, will most likely mean that nasty encounters with odd behavioural patterns and bad habits will be few and far between.
Arianna opines: ‘The surest sign that my ex and I have reached a better place is a newfound willingness on both our parts to not let our pet peeves get in the way of our having a good time. Even in the happiest of marriages, there are little things that each partner does that inevitably set the other one off. These annoyances are magnified ten-fold when you are no longer together as a couple - which is why making an effort to avoid them is one of the secrets of a good divorce.’
It couldn’t, therefore, have been easy being Indian textile heir Arun Nayar, who up until a few months ago, was Mr Elizabeth Hurley.
During his marriage to the model, actor Hugh Grant - his wife’s former love of thirteen years - was a ubiquitous presence on family holidays.
While he most probably didn’t attend them all, one can only assume that Hurley’s desire to have both her husband and ex-boyfriend – who is godfather to her son Damian - on the same trip, would have proved uncomfortable. At least for someone, anyway.
‘If I'm alone with Hugh, Arun and Damian,’ the beauty once claimed, ‘I can turn off my cell phone. No one else really matters.’

Ubiquitous presence: Elizabeth Hurley with her now estranged husband Arun Nayar in St Tropez in 2008, and her ex-partner Hugh Grant on the same trip

The union, in any case, was not to last. Arun and Liz announced their split in December.
‘Like marriage, divorce isn’t easy either,’ explains Arianna, before revealing that her estranged husband sent her a bouquet of flowers and a card on the day that would have been their 20th wedding anniversary.
A strange gesture, perhaps, but then the Duke and Duchess of York, who only months ago were left red-faced as it was revealed Fergie had attempted to sell strangers money-spinning access to her husband, continue to live together at his home, Royal Lodge.

‘Little by little,' Arianna continues, 'with a lot of hard work, we've grown closer and closer. We have gotten to the point where there is really nothing left to work out - and it feels completely natural to be able to sit on a beautiful beach or stroll through the lovely streets of Agios Nikolaos together.’
Who is to say that what enabled Pippa and George to pound Spanish promenades so happily together a few weeks ago was a result of a similar post-end-of-relationship serenity. After all, theirs is said to have only ever been a short fling.
Perhaps it would be almost too cynical to suggest that their Spanish jaunt had helped Pippa land the job she was reported to have picked up at his environmental firm last week. Then again, perhaps it helped push things along.

Relationships for life: Liz and Hugh when they were still together in 1999 (left) and Bruce and Demi at the Emmy Awards in 1997

From bum-lifting and fake tan products, the interest bestowed upon the Duchess of Cambridge's party-planning younger sibling, has made the 27 year-old an invaluable marketing tool for companies around the world.
And so when photographs of her smiling broadly on holiday with her ex – despite having a devoted boyfriend, in the form of former England cricketer Alex Loudon, back at home – ‘Perfect Pippa’ is just one other ‘celebrity’ defying the long-established rulebook that exists over holidaying with one’s ex.
'It’s completely fine for former lovers to behave and act in a way that is uniquely comfortable to them,' says the expert.
'Few outside anyone’s tight bubble may understand, but just as intimate their engagement or very initial first date might have been, the same would go for the subsequent split. It only makes sense to them.'
Perhaps, then, there’s no rule book at all.