Margaret Thatcher barely mentioned the plight of Nelson Mandela when she controversially invited the hardline South African president PW Botha to talks at Chequers on 2 June 1984, newly released Downing Street files show, throwing into doubt claims made after Mandela's death last month.

Two of Thatcher's closest supporters, Norman Tebbit and Charles Moore, claimed on Mandela's death that as prime minister, she had put persistent pressure on Botha to release Mandela. Moore claimed that "the release of Mandela was the strongest and most specific of all her demands".

But there is little evidence in official papers to back this up. The Downing Street file on the visit shows Thatcher did not raise Mandela's case at all during the four-hour official meeting at Chequers.

She did, however, mention Mandela during a private 40-minute discussion before the official meeting started, but this was only in a context that made it seem as if the imprisonment of the African National Congress leader was on a par with the case of four South African officials from Armscor, the state-owned weapons manufacturer, and four members of a Coventry engineering firm who had been charged in Britain with breaking the UN arms embargo.

There were no official notetakers during the private discussion, but Thatcher gave her private secretary an account of the meeting that shows Botha raised the case of the four Armscor officials; she responded that it was a matter for the courts and that there was nothing the government could do.

Thatcher then raised the case of Nelson Mandela. The minutes show that the South African president replied with a similar formula: Botha said he noted the prime minister's remarks, but was not able to interfere in the judicial process.

He also unsuccessfully pressed for the ANC office in London to be closed. The prime minister replied: "We could not do this under our law and there was no evidence that the office personnel had been guilty of illegal activity."

Thatcher did raise the proposed forced resettlement of thousands of black people of the KwaNgema community in the eastern Transvaal at the meeting. She also told him that it was "totally unacceptable" for political rights to depend on the colour of a person's skin. Botha replied that he had made clear in the South African parliament that he was against forced removals, but that it was never possible for South Africa to satisfy international opinion. The two leaders also discussed the security situation in Namibia and Angola.

Thatcher's Foreign Office briefing papers for the meeting say: "We have supported calls for Mandela's release. His standing among blacks in South Africa is unrivalled."

The Downing Street file also includes the Foreign Office assessment of Botha as "a hard, dour and belligerent professional Afrikaner politician" who could be "disagreeably rude". It also shows that the Foreign Office had evidence that South African intelligence was involved in a break-in at the London offices of the Anti-Apartheid Movement.

Botha's visit to Britain had been fiercely opposed by a number of African leaders. Their letters to Thatcher are contained in the file. The Tanzanian president, Julius Nyerere, wrote to her in May requesting that "you will be able to prevent Britain's usual courteous reception to foreign leaders from being misunderstood by indicating, both publicly and privately, Britain's strong opposition to South Africa's aggressive policies towards other African states, as well as to apartheid itself".

Around the same time, the prime minister agreed to meet the president of the Anti-Apartheid Movement, Bishop Trevor Huddleston.

An earlier Downing Street file records the need to remind the Thatcher family about political sensitivities in South Africa. There is a note referring to Denis Thatcher's proposed visit to South Africa, which advised him against attending a cricket match between South Africa and the West Indies.

Thatcher eventually met Mandela at No 10, after he had been freed from prison, in July 1990. They shook hands and posed for photographs on the doorstep.