My post of July 15th below shows two graffiti images from the old mail sorting office on New Oxford St/Museum Street. I saw today that they have been joined by more. The tall banner seems suitably disrespectful, with a young Queen Elizabteh holding a spray can and wearing a CND brooch. And yet the banner itself, with its size and professional fixing, almost seems like a piece of corporate advertising. The signature of Mr Brainwash, in the bottom right hand corner perhaps confirms the rumours.
I don’t know the authorship of the other two.