Both feature in the book and yes I visited them years ago....
St Stephen Walbrook has a saxon foundation but was destroyed in the Great Fire of 1666. It was rebuilt by Christopher Wren and damaged during the blitz. The large altar was carved by Henry Moore..
The Starbuck is incongruous don't you think?
Detail from top of Bank of England.
St Margeret Lothbury is another church destroyed by the Fire and rebuilt by Wren.