Did a pair of twins really marry?

It is a story that made headlines all over the world, often told in a very colourful way. Here, for instance, is a recent example from Canada:

A member of the British House of Lords recalls being told by a judge about an astounding incident in which a man and a woman who were both adopted met each other, felt an instant attraction and decided to get married.

It wasn't until they sought information about their birth parents that they discovered the sickening truth - they were actually brother and sister, twins who had been separated at birth, adopted by different parents and never told of each other's existence. When they met by accident, they didn't realize their attraction was more familial than amorous.

Yet in this morning's Guardian Jon Henley asked the question that has been worrying me for the past few days. Is the story actually true?

As he points out:

it all came from a single remark more than a month ago by the vehemently anti-abortion Roman Catholic peer and father of four, Lord Alton, in favour of all children having the right to know the identity of their biological parents.

He had heard about this particular case, he said, from the judge who handled the annulment. Or perhaps (he later admitted) a judge who was "familiar with the case". Britain's top family judge, Sir Mark Potter, has never heard of the story. And, as the excellent Heresy Corner blog notes, the whole thing is statistically improbable, procedurally implausible (for 40 years, adoption practice has been to keep twins together) and based on the equivalent of a friend in the pub saying, "Hey, I heard the most amazing story the other day."

I still have a soft spot for David Alton. If only because, long ago, as secretary of York Liberal Students I twice invited him to speak to our group. In those days he was one of the party's great radical heroes. So I don't want to impugn his integrity.

And you don't have to be a Roman Catholic to wonder if it is a good thing for somone's commitment to fatherhood to begin and end with masturbating into a testtube. (Why, incidentally, does Henley tell us that Alton is a father of four if not to say "look at these Catholics and all the children they have"?)

But two truths have to be admitted.

The first is that it is not unknown for anti-abortion campaigners to tell horror stories that turn out not to be true upon investigation.

The second is that judges tell all sorts of entertaining anecdotes - particularly after the port has been round a couple of times - but that does not mean they are the gospel truth.