I believe all of this will come down to a paper trail in the fact that WAS there a legal & legitimate sale of the copyright to Joe Francis which in turn there would be paperwork from him to the NOC. From what I have read the copyright covers among other things, illustrations, which is the "drawings". The copyright lasts for 70 years after the death of the person/owner/business whose work(s) it was - I may be wrong on business but person(s) for sure; and that would be 70 years after the last surviving if more than one.
I would definitely be sure that I had all the legal transactions "paper trail" in order before I went to court.
Much better to keep the family together and work all this out of court. Maybe NOC turn it over to AN and NOC members get discounts on parts, services, etc.? Or vice versa......??
https://www.gov.uk/guidance/license-sell-or-market-your-copyright-material