I spent quite a lot of May and early June in Central London.
On a walk a couple of months ago, a friend mentioned that the backstreets of Westminster are worth walking around. A few weeks later, we followed the Westminster Hidden London walk.
You see many iconic sights: St James (and its Pelicans), the Houses of Parliament, MI6 building, Big Ben, and other places on the map above.
We were lucky to be allowed to see the basement of Morpeth Arms pub. This is not open to the public but one of the bar staff took us downstairs and told us its history. The basement (which is at street level on the side opposite the entrance) has a cellar. Prison wardens who once occupied the building took prisoners to the Thames through the tunnel in the cellar. The ghost of a prisoner who died in the basement haunts the pub!