The cache container is obviously not hidden at the posted coordinates, but you will be seeing a lot of this building in your quest to find it. This is a cross between a mystery and a multi; the mystery element is working out where to find the clues!
St Paul's Cathedral is Christopher Wren's masterpiece, designed to replace the cathedral destroyed in the Great Fire of London. Constructed during the late 17th Century, the cathedral's iconic domed roof has become one of the most recognisable structures in the city. It somehow survived the Blitz in the 1940s and it has almost come to symbolise London itself. Indeed, views of the cathedral are officially protected in London through strategic planning policy, which seeks to ensure that new development maintains clear sight lines to the dome in defined long-range views across London. You won't need to visit any viewing locations in outer London for this cache, although I highly recommend doing so at your leisure: Parliament Hill, Alexandra Palace, Greenwich Park, Nunhead Cemetery and King Henry's Mound in Richmond Park are some of the surprisingly far away places from which you can perceive the dome!
The task:
I have taken 5 photographs of some of my favourite views of the cathedral. All are in central London to make the task manageable.
The photos were taken on my phone. All you have to do is place yourself exactly where I have taken the photograph and answer a question when you're there. Most of these won't be too challenging if you know London well.
Unfortunately the original Stage 4 appears to be permanently closed to the public so I've replaced this stage and updated the formula. Message me if you were halfway through the old puzzle!
Stage 1

Once you are in place, look down at your feet and note the four digit number on a round plaque. This is 12AB.
Stage 2

When you are standing in place, look to the entrance of the alleyway on the left, where you will find a plaque on the ground celebrating an industry for which this street is well known. The date of this edition is April CD 1900
Stage 3

At this point, look up to the wall on your right and you will see a metal plaque. There is a phone number on this plaque giving you E and F: 020 EE9EF465
Stage 4

Near this location there is a cover for a Thames Water meter on the pavement. You need two numbers for G and H : ISO G0H3
Stage 5

Here, look to your left where you will see a bronze seated statue. The statue was erected in 20JK
The cache can be found at:
N51 FB.E(H-G)C W000 (K+F).(H+G)JA
Good luck and I hope you enjoyed the views!