In June 1986, in a political deal with Prime Minister of New Zealand David Lange, presided over by United Nations Secretary-General Javier Pérez de Cuéllar, France agreed to pay NZ$13 million (US$6.5 million) to New Zealand and apologise, in return for which Alain Mafart and Dominique Prieur would be detained at the French military base on Hao Atoll for three years. However, the two agents had both returned to France by May 1988, after less than two years on the atoll. Mafart returned to Paris on 14 December 1987 for medical treatment, and was apparently freed after the treatment. He continued in the French Army and was promoted to colonel in 1993. Prieur returned to France on 6 May 1988 because she was pregnant, her husband having been allowed to join her on the atoll. She, too, was freed and later promoted. The removal of the agents from Hao without subsequent return was ruled to be in violation of the 1986 agreement.