Tyre Widths

[JontyR]

Someone asked a question on one of the pages I subscribe to on FaceBook about tyre widths and rather than sift through those that actually don't know, I thought I would ask on here in the hope I get a sensible answer

Is it legal to run a wider tyre on the front than on the rear?

There is no point in asking why...because I don't know either, but the general consensus is that it isn't legal.