London supports a large population of celebrities and famous individuals. These are subdivided into a complicated ranking system, which is organised with consideration for their genre, medium, and role. At no point does level of skill1, appear to be a factor to their placement. Visitors to London should, however be aware of the correct procedure to follow upon recognising a famous individual or celebrity upon the streets of the great metropolis.
Overcome initial instinct to stare.
Adopt nonchalant attitude - as if you are in the company of such people all the time.
Optional: If the celebrity is a minor one, ignore any looks or motions from them as they try to decide if you have recognised them or not.
If necessary, indicate to your companions the presence of the celebrity through an inaudible whisper or barely-disguised pointing.
Enter phase of thinking you are mistaken.
Upon exit from vision of celebrity, commit to memory time and location of sighting, then bore friends and relatives with detailed account of your brief encounter.