 However, following the acceleration of the US UGM-133 Trident II missiles, Thatcher wrote to US President Ronald Reagan in 1982 requesting the United Kingdom be allowed to procure the improved system instead.An agreement was made in March 1982 between the two countries, and under the agreement, Britain made a 5% research and development contribution.Beginning in 1985, both HMNB Clyde and the Royal Naval Armaments Depot Coulport at Faslane underwent extensive redevelopment in preparation for the "Vanguard" class submarines and Trident II missiles.