Unacknowledged borrowings from 'The Assassin' ('52)?
This movie plays like an adaptation of the British Noir The Assassin (1952).
A Brit ends up running around Europe (or Venice) trying to uncover the plot of a cabal of baddies; a politician is taken out, and the villain is pursued across rooftops in the final setpiece.
Very strange for 1947, it's actually filmed on location. It looks pretty good. Michael Todd even looks much like Clive Owen, back in the day.
He also seems like the early template for James Bond.
You can see it on Netflix streaming, currently.