The UK radio manufacturers had to pay a royalty of £1 per valve holder to the British Valve Association to cover use of their members' patent rights. Further, they dictated that not more than one electrode structure could be contained in a single envelope (which would have evaded the royalty - at least in part). The Americans appeared to be driven by the desire to produce a low-cost 'every expense spared' design which was to lead to the All American Five.