This is for people who've been to London or intending to go for the first time. It can also be for Londoners returning from abroad as well.
What is it that when you experienence it finally made you feel like that you were in London. It could be a sight, or for more regular visitors, a sound or even a smell that finally makes you think "Yes, I'm in London" or for Londoners, "Yes, I'm home" or more likely "No, I'm home and it's work tomorrow".
For instance, when I went to Sydney and saw the Opera House and the Harbour Bridge, I knew I had finally arrived because these are unique to Sydney and in Paris, it was seeing the Eiffel Tower. And when I return home, it is the tube journey that brings me back to reality.
So, over to you....