Hiding in the basement

Some time ago I heard a rumour about something exciting ( to me) bricked up in the basement of a building in Nottingham, Now you have to remember that Nottingham had a reputation for lace and there used to be many lace factories in and around the city centre and I have an interest in hand made lace.
A week or so ago I was invited to visit the building and see the basement, I was also advised not to upset the resident ghost too much.

This is what I found.

                                                                                             hidden behind the door.