Its a .............

Mystery............ this is by St. Martins in the Fields at Trafalgar Square, these words always catch my eye as I walk past. I was going to write a few words on exactly what and where it is etc but its way too late, I may edit tomorrow and will certainly catch up on comments very soon, night all :)

*edit* the word is from a poem created by Andrew Motion to encircle the light well in the crypt here