 Britain and France came to a mutual agreement to serve as the join lead nations on the envisioned programme, while also recognising that other partner nations would be necessary.Both France and Britain approached various other nations to join on the collaborative programme, however negotiations with interested nations were often protracted, in part due to there having been a prevailing attitude of scepticism; author C.N.Hill stated that "many countries thought that the U.K. was seeking to foist an obsolescent launch vehicle on them, and making them pay the costs".