Thames Anglers Conservancy - or Anglers'?

[willow]

OK pedants - which is correct? It is not the conservancy wing of an organisation called the Thames Anglers, it is an organisation that goes by the name of Thames Anglers Conservancy - but should it still be s'?

There is no organisation called Thames Anglers, btw, if that helps. I am bloody confused.

Anglers'

That's what I thought, but then thought it wouldn't be Thames' Conservancy, so why is it Thames Anglers' Conservancy. Anyone care to explain?

It is the conservancy that protects the Thames for the use of anglers plural.
If it was the conservancy for the protection of the Thames...well, that's singular and single possessives don't have an apostrophe

Tx