Pre-WWII Subcontracted Aircraft Manufacture and Intellectual Property

[Steve Brew]

Bit of an odd query, perhaps, but I'm wondering if anyone has any knowledge of the workings of IP with pre-war outsourcing of aircraft manufacture?

For example, Armstrong-Whitworth outsourced Siskin IIIA production to Bristol, Blackburn, Gloster, and Vickers, as they were presumably at capacity with concurrent deliveries contracted for both the Siskin and the Atlas.

I understand it was also government policy at the time to spread contracts amongst firms to keep them in business and to retain trained staff, to facilitate a rapid, industry-wide response to surge requirements, in an emergency, but how did competing companies protect their designs?

I'm not seeking a detailed legal run-down, rather just a basic explanation for my own understanding, if someone else has looked into the subject in the scope of their research...?

Thanks
Steve