An acquaintance, Sarah, 39, told me recently that her new boyfriend, Charlie, had pulled her up on her flirtatious behaviour. “He loved me flirting with him... he must've known I'm a natural-born flirt,” she protested. No, I told her, Charlie assumed he was so irresistible she flirted only with him, and was perturbed to find that she flirts outside of their cuddly new coupledom.

In fact, I informed her, new research has found that being around flirtatious women can make a man less appreciative of his partner. Oh yes, men love a flirt when they've just met someone - it stands a good chance of turning his head. But put the brakes on that kind of behaviour once you two are together! In his eyes, there's a world of difference between flirting directed at the oh-so-wonderful him and an entire flirtatious personality.

This is the result of typical territoriality, it seems. You might think a man would see a flirtatious partner as reflecting well on him “Isn't she so sexy and sparkling?” such a man would ask. “And I've nabbed her,” he might silently gloat.

However, there must be a deeply rooted belief in most that the sexy flirt they have “captured” should then morph into a down-to-earth, completely trustworthy partner. Because ultimately, continuing flirtatiousness must seem threatening.

And any woman who's claimed not to care that her partner's a flirt is simply putting on a brave front. I've been told time and again by women in relationships with flirts how they'd love to throttle him when he dabbles in flirting, say, at a party. And although looking daggers at him might curb his enthusiasm, they still feel oceans of resentment towards the women on the receiving end.

So enjoy that flirting in your relationship, but be wary of proclaiming yourself a natural-born flirt, with every right to continue flirting your way through life, once in a partnership. It may be that you go from flirt to finished in the wink of a flirtatious eye.

Times recommends

• Pity the poor (other) woman
• It was all too easy to lose my son
• Video: How to do party make-up