After a brief period as part of the West Indies Federation (1958–62), the islands became an associated state with full internal autonomy in 1967. Both Nevis and Anguilla were unhappy at St Kitts' domination of the federation, with Anguilla unilaterally declaring independence in 1967. In 1971 Britain resumed full control of Anguilla and it was formally separated in 1980. Attention then focused on Nevis, with the Nevis Reformation Party seeking to safeguard the smaller island's interests in any future independent state. Eventually it was agreed that the island would have a degree of autonomy with its own Premier and Assembly, as well as the constitutionally-protected right to unilaterally secede if a referendum on independence resulted in a two-thirds majority in favour. St Kitts and Nevis achieved full independence on 19 September 1983. Kennedy Simmonds of the PAM, Premier since 1980, duly became the country's first Prime Minister. St Kitts and Nevis opted to remain within the British Commonwealth, retaining Queen Elizabeth as Monarch, represented locally by a Governor-General.