I became interested in red pillar postboxes after reading about them in a book about London street furniture. I was intrigued to see how many pillar postboxes in Stoke Newington might be considered rare. More generally, I was also interested to see the number of postboxes by Royal Cypher, which gives a rough indication when the postbox was installed.
You can read more about this little project in article I wrote in the Hackney Gazette.