I bring to the problem a mind totally unencumbered by theory. In other words, I haven't a clue what I'm talking about. But it occurs to me that there are certain fields that must be completed on a web form. I believe (perhaps wrongly) that it's possible to hide fields from human view but not from robots. Therefore, assuming "name" is compulsory, would it be possible to have four fields, namea, nameb, namec and named, all in the same place but only one of which, chosen at random, is visible to the human? Anything filling in one of the hidden fields would have to be a robot.

If I've wasted anyone's time with a daft idea, I apologise.

Regards,

John Davies