Classic Cotton-Gabardine, how much water-resistant in real?

[Trenchfriend]

In the old movies, like "Casablanca" or "Breakfast at Tiffany's", I can not exactly see, how much the Trenchcoats are soaked with water.

Are here any experiences with Gabardine-Coats and heavy rain?

I've got a modern times raincoat of Hugo Boss, with 55% Polyester/45% Cotton and it's really heavy water-resistant (not waterproof!), but what about old fashion Gabardine?

 

[Big J]

My trench coat is 100% cotton, with an oilskin lining under flannel. Very good!