This is a snippet out of a 1926 Rover 9/20 parts manual. Note the differential has a mix of metric and Imperial bearings in it.Heaven help us! Whitworth bolts from Slough? Live and learn....
Renault managed metric banjo bolts and securing bolts (10mm spanner) on the English spec. Lockheed drum brakes on 4CVs and Dauphines. The master cylinder and wheel cylinder IDs are all Imperial sizes like 13/16" and metric sizes just don't work. They have 7" and 9" drums respectively, expressed in exact mm sizes in the manuals. (Not relevant but amusing to note that a Dauphine had the same diameter drum brakes as an FJ Holden.)