Former President F. W. de Klerk, who announced his decision to retire from the political arena yesterday, was a little known Afrikaner leader until his decision in February 1990 to un-ban the African National Congress and release its imprisoned leader, Nelson Mandela.

These two successive decisions, made within a momentous week, catapulted Mr De Klerk on to the world stage, in part because of the international fame of the prisoner that he set free and in part because it contradicted stereotypes of the stubborn Afrikaners who had led the governing National Party since it captured power in 1948.

Within days he gained world recognition as a reformer, comparable to Mikhail Gorbachev. His image was simultaneously enhanced briefly in the black townships, where young blacks referred to him as "Comrade De Klerk". Mr Mandela initially praised him as "a man of integrity".

Mr De Klerk had to pay a price, however, within the ranks of the Afrikaner community: conservatives branded him a volksveraaier or traitor to his people. While publicly Mr De Klerk shrugged his shoulders at the epithet, it must have hurt. He came from a conservative Afrikaner family: his father, Jan de Klerk, served as a cabinet minister under three Afrikaner Prime Ministers, J. G. Strijdom, H. F. Verwoerd and B. J. Vorster. His brother, Willem, was one of Afrikanerdom's premier intellectuals.

Mr De Klerk, who was born in March 1936, soon found himself in the line of fire from the ANC leadership; he was accused of talking peace but planning for war and charged with complicity in the violence which swept over South Africa during its transition to democracy.

A critical point was reached in June 1992 when residents in the black township of Boipatong, near Vereeniging, were attacked and murdered by Zulu-speaking occupants from a nearby hostel. Mr De Klerk was blamed by the ANC for the massacre of at least 40 people, including women and children.

When he visited the township a few days later, his vehicle was surrounded by angry residents who threatened to attack him. Protected by bodyguards, he was forced to leave hastily. From then on, Mr De Klerk's chances of winning a significant share of the black vote for his National Party in the coming election were minimal.

While the National Party was not disgraced in the general election of April 1994 - the first fully democratic election - it won only a minute share of the black vote. Its main support came from the minority communities: the whites, coloureds and Indians. Its 20 per cent share of the vote entitled it to a commensurate share in the government of national unity, which was formed under the interim constitution.

Mr De Klerk served as Deputy President for a year when, to the surprise of many political observers, he persuaded the National Party to withdraw from the government of national unity, thus apparently jettisoning the hours of hard negotiating devoted to securing a place for his party in the first post-apartheid government.

Mr De Klerk, who was first elected to parliament in 1974 and who was first appointed to the cabinet four years later, was initially seen as a conservative within the National Party, a man who agreed to reformist measures reluctantly rather than enthusiastically.

One reason for that may have been his succession to the provincial leadership of the party in the old Transvaal in 1982 after conservatives in the party, dismayed by the reform policies of Prime Minister P W Botha, broke away to form the Conservative Party.

With the National Party under increasing attack from the Right and losing a string of by-elections to the Conservative Party, Mr De Klerk sought to retain white support, particularly within the Afrikaner community, by reassuring them that the National Party would not embark on radical reform.

But Mr De Klerk, a devout member of the smallest of the three Dutch Reformed Churches and a lawyer by training, was renowned for his logicality: when he realised that apartheid, or separate development, was not a viable policy, he moved steadily, if prudently, away from it, accepting the reforms introduced by Mr Botha rather than breaking away to join the Conservative Party under Andries Treurnicht.

When he succeeded Mr Botha as president in September 1989, Mr De Klerk felt free to proceed more quickly. Hence his astonishing decision - as it seemed then - to unban the ANC, release Mr Mandela and seek a negotiated settlement. A major factor in his decision was the collapse of communism in Eastern Europe. He believed that it would weaken the ANC because of its close ties with the South African Communist Party.

The past year was a tough one for Mr De Klerk. He has had to witness a steady decline in support for the National Party from the 20 per cent it won in April 1994 to below 15 per cent. At the same time, he had to face renewed charges of having surrendered to the ANC during the negotiations.

These charges did not come from rabid Afrikaner nationalists and white supremacists but from respected intellectuals. Thus, an editorial in the Afrikaner newspaper, Die Burger, accused him of failing to protect the Afrikaans language and culture, and virtually charged with cowardice.

At the same time, there were increasing suspicions that he knew of, but turned a blind eye to, atrocities committed by the security forces during the struggle against apartheid. These suspicions, vehemently denied by Mr De Klerk, were articulated, albeit obliquely, by the chairman and deputy chairman of the Truth and Reconciliation Commission, Desmond Tutu and Alex Boraine.

Their remarks, made after Mr De Klerk's second appearance before the commission, stung, so much so that the National Party first demanded an apology and then sought a high court injunction compelling Archbishop Tutu not to prejudge the findings of his commission and ordering Dr Boraine to resign for his bias.

Another setback occurred in May, when Roelf Meyer, the man identified as Mr De Klerk's successor, resigned from the National Party to found the New Movement Process. Mr Meyer's decision to resign came after his position as head of a special task group mandated to chart a way forward for the National Party, was abolished by Mr De Klerk.

Mr Meyer's new movement contributed to Mr De Klerk's woes by attracting members of the National Party into his ranks, resulting in its loss of control of the Pretoria City Council and its image as a party on the skids.

Throughout these troubles, however, Mr De Klerk maintained a brave face. As recently as May, he told The Irish Times that the National Party was attracting strong support in the black community and that it would succeed in reducing the ANC's majority in the 1999 general election.

Talking of retirement then, he said: "As long as they want me, and as long as I have the energy and health to do so, and the belief that it's in the best interests of the party and the country to stay on, I shall stay on."

Yesterday, however, he said: "The time has come for me to retire from active politics . . . I wish to open a door for the National Party to provide further proof of its dynamic break with the past."