P W Botha was invited to talks with the Thatcher at the British prime minister's Chequers country residence to discuss South Africa's policy towards its black population, as the apartheid regime sought to emerge from its international isolation.
The record of that meeting, released 30 years later under secrecy rules, showed that Thatcher pressed Botha on the issue of apartheid but Mandela's name did not come up during the official talks.
The newly declassified official records show that the British government confirmed that Mandela's imprisonment was raised at a short "tete-a-tete", but that Thatcher made little progress with Botha.
In a note about the 40-minute private meeting sent to the Foreign Office on June 2, 1984, Thatcher's advisor John Coles wrote: "The prime minister said afterwards that Mr Botha had stated that it was never possible for South Africa to satisfy international opinion.
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"She took the opportunity to raise the case of Nelson Mandela.
But in the broader, four-hour meeting where official minutes were taken, Thatcher omitted the leaders' disagreement over anti-apartheid hero Mandela -- despite prior guidance from the Foreign Office to make the point.
In a briefing paper written by the Foreign Office for the prime minister's office ahead of the meeting, it was suggested that Thatcher include Mandela's release from prison as a "point to make".
In a statement to the House of Commons, the lower house of parliament, after the meeting, Thatcher said: "On the internal situation in South Africa, I expressed our strongly held views on apartheid.