thick as a London fog

Translations
густой как лондонский туман
The mystery was as thick as a London fog.
Тайна была густой как лондонский туман.
Definitions
A phrase used to describe something that is very dense or difficult to see through, often referring to a situation or atmosphere that is confusing or unclear, similar to the heavy fog that can envelop London.
Words
fog

noun
туман
thick

adjective
толстый
London

proper noun
Лондон