compound noun VS possessive case

[hela]

Dear teachers,

Would you please tell me why we do not say "London's marathon" but "London marathon" instead?
Are there rules that tell you when to use compound nouns instead of the possessive?

Many thanks
Hela

 

[bhaisahab]

Dear teachers,

Would you please tell me why we do not say "London's marathon" but "London marathon" instead?
Are there rules that tell you when to use compound nouns instead of the possessive?

Many thanks
Hela

It's called The London marathon.

 

[5jj]

Are there rules that tell you when to use compound nouns instead of the possessive?

The simple, if not very helpful, answer is 'No'.