The Cache is not at the posted coordinates! It is nearby though.
You must complete the associated adventure lab get the lab bonus codes.
The Lab cache involves a decent walk but there are plenty of other caches and Lab caches to do in between and there is no need to do it all at once. In any event, it's hardly an ordeal to walk through London and you are an intrepid geocacher after all! Or, you could always take public transport. As I said in the Lab cache description, it's not easy to get to Australia!
Use the codes to find the cache.
N51 AB.DDC W000 BD.EBA
There are lots of muggles everywhere in London. Extreme stealth please.
Your adventure can begin after downloading the Adventure Lab app from Groundspeak.