( Tragically , UNCN Bernt Carlsson was not present at the signing ceremony . He was killed on flight Pan Am 103 which exploded over Lockerbie , Scotland on 21 December 1988 '' en route '' from London to New York . South African foreign minister Pik Botha and an official delegation of 22 had a lucky escape . Their booking on Pan Am 103 was changed at the last minute , and Botha , together with a smaller delegation , caught the earlier Pan Am 101 flight to New York . ) UN Security Council adopted resolution 632 on 16 February 1989 requiring that implementation of UNSCR 435 should officially start on 1 April 1989 . AG Pienaar , under the supervision of UN Special Representative Martti Ahtisaari who arrived in Windhoek in April 1989 to head the United Nations Transition Assistance Group , began Namibia 's transition to independence . The transition got off to a shaky start because , contrary to SWAPO leader Sam Nujoma 's written assurances to the UN Secretary-General to abide by an agreed cease-fire and repatriate from Angola only unarmed Namibians , the South Africans alleged that approximately 2,000 armed members of the People 's Liberation Army of Namibia ( PLAN ) , SWAPO 's military wing , crossed the border from Angola in an apparent attempt to establish a military presence in northern Namibia . Under pressure from AG Pienaar and South Africa 's foreign minister Pik Botha , UNTAG 's Martti Ahtisaari took advice from British Prime Minister , Margaret Thatcher , who was visiting Southern Africa at the time , and authorised a limited contingent of South African troops to aid the South West African Police ( SWAPOL ) in restoring order . A period of intense fighting followed , during which 375 PLAN fighters were reported to have been killed
flight Pan Am 103
Pan Am Flight 103
Louis Pienaar