Ah, exes. You’ve shared the worst of times, and the best of times. Mostly, at the end of a relationship, it is the worst of times, played out to a soundtrack of slamming doors, shrieked accusations and flying candlelabra. Which makes it so very baffling why some people remain on such good terms with their ex-partners and spouses.

On the celebrity front, Chris and Billie are joined by Sadie and Jude, Fergie and Prince Andrew and – the reigning monarchs of comfortable ex-ness – Liz and Hugh. Sadie and Jude have triumphed over his adultery to holiday together; Fergie has invited Prince Andrew’s new partners to their children’s birthdays.

Liz and Hugh, however, show that progeny is not required to maintain a platonic relationship. Grant may not have made it up the aisle, but Hurley rated him highly enough during their 13 years together to appoint him godfather to her son Damien, and usher at her wedding to Arun Nayar.

Is it healthy to hang on to an ex? Angela Neustatter, the author of Relationships and Sex, to be published in 2008, says: “Exes are very interesting, particularly if they are now happy with someone else. There is often a frisson as you think, could they have been happier with me? And a slight edginess about where they fit in to your life. At best what one gains is being friendly with someone you know very well . . . At worst you find out really they are a bit of a scumbag and you feel slightly seedy that you ever could have allowed yourself to give yourself to them."

And there is the thorny matter of whether you or your ex is still harbouring secret desires. Neustatter does not recommend maintaining contact with an old flame who never wanted to be extinguished in the first place.

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