Yes! Yes! Er - what was your name again?

It's the morning after and you have not got a clue where you are or who they are or what you have done. But now forgetful lovers have the perfect excuse - all they have to do is tell their partners: "Sorry, I must have been suffering from recurrent coital amnesia."

It may sound like a state of mind induced by one too many bottles of chardonnay. But, according to the Journal of Neurology, Neurosurgery and Psychiatry, this medical condition, characterised by sudden and dramatic memory loss after sexual intercourse, is not an uncommon clinical occurrence.

Doctors in a letter to the journal recount the case of a man in his sixties who frequently suffered bouts of amnesia after sex. "During these events he would repeatedly ask questions such as `What are we doing?' `What time of year is it?' `What time of day is this?'" reported Dr Russell Lane of the West London Neurosciences Centre.

The memory loss lasted for 30 to 60 minutes on each occasion, after which he recovered perfectly except for the fact that he had no memory of intercourse and only the haziest recollection of foreplay.

Although he seemed aware of experiencing difficulties during the amnesia attack, the doctors found his activities during intercourse and after were "unremarkable". Investigations showed nothing except an irregular brain signal which doctors attributed to migraine.

Recurrent coital amnesia is thought to be one type of a more common condition known as transient global amnesia (TGA), which happens during periods of physical and emotional stress. It is characterised by the sudden development of amnesia usually accompanied by repetitive questioning but without any other alteration in consciousness or any obvious neurological disturbance such as an epileptic fit.

"The fact that a person can repeatedly experience selective amnesia for sexual intercourse, but otherwise function normally during the amnesic period, raises interesting social and medicolegal considerations," Dr Lane said. Or, as agony aunt Clare Rayner puts it rather more forcefully: "What a glorious new excuse - `Sorry, I forgot all about it, darling'."