Looking on the internet deeply has found these results:

I will go in London is the most popular phrase on the web.

I will go on London 11 results on the web	I will go in London 1310,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
In that case, you and I will go to London to see this man. As much as I dread it, I think I will go back to London. I will, when we go to London. Then I will go on dying for perhaps another 60 years. To give it to him, you and I will need to go to London. So I go to London where I do much photographic work. I will go on my way About our marriage... I will go back to London and draft a plea of forgiveness for you to submit to the King.	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

I will go on London

11 results on the web

I will go in London

1310,000 results on the web

More popular!

In that case, you and I will go to London to see this man.
As much as I dread it, I think I will go back to London.
I will, when we go to London.
Then I will go on dying for perhaps another 60 years.
To give it to him, you and I will need to go to London.
So I go to London where I do much photographic work.
I will go on my way About our marriage...
I will go back to London and draft a plea of forgiveness for you to submit to the King.

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.