https://spitalfieldslife.com/2022/09/29/the-return-of-sue-hadley/
I will try and see if I can find the staircase in the first picture, it'll have a security lock on the door nowadays, but there are a few tricks to getting past vthos I know from years of carrying out letter drops.
A name is mentioned in the text, Angela Burdett Coutts, she seems to have been a one lady charity phenomenon, there are so many things connected with her all over the borough. Coutts is the royal family's personal bank. I don't think they do cash machines though.