Ghost??? in St Mary's Guildhall

I stumbled on the the other night. Does anyone know anything about it? Has it ever been explained?

The best explantion I've read is that it's an optical illusion created by two people with dark hair, a man standing behind a woman and the woman is holding a child who is standing on a chair facing backwards. The illusion is enhanced by the speckle-effect of a newspaper print process.

This could easily be proved by someone providing the original photographic print which of course is not going to happen!

Thanks guys