Traduko - Bosnia lingvo-Angla - sljedećim tekstom ću objasniti zašto ...

The following text will explain why I´d /would like to visit London.

Thank you for your suggestion. I think that your proposal to the translation somewhat changes the meaning of the requested sentence...

it should be in the next text, not in the next letter.

Thanks, for your opinion. Like I already explain I opted for:"in the next letter" rather than "in the next text," becuse it is obvious that she/he is writting a letter. Thanks.

a_destiny's translation is good. I was thinking the same thing.