By Barnaby Phillips
BBC News, Cape Town
Mark Thatcher looked very nervous as he took the witness stand and swore on oath at a court in Cape Town, where he was questioned about a failed coup attempt in Equatorial Guinea.
Thatcher has been co-operating with authorities in South Africa
As the session progressed, it became obvious that he was very familiar with all of the 43 questions submitted by the Equatorial Guinean government, and had worked out his answers.
One of the questions was written in garbled English and featured misspellings of some of the names of others linked to the plot.
The South African magistrate insisted on reading them out that way, claiming it was not up to her to change them.
Despite his nervousness, Thatcher's answers were very consistent.
The son of former British Prime Minister Margaret Thatcher admitted knowing many of the people linked to the plot.
One of them was Simon Mann, jailed in Zimbabwe on charges related to the coup attempt.
He said they first met in a Cape Town waterfront pub in 1997.
Their last meeting was in February 2004, when they celebrated Simon's wife becoming pregnant.
This was only a couple of weeks before Mann's arrest, but Thatcher insisted that he and Mann never discussed a coup plot.
Thatcher confirmed that he met Nick Du Toit, now in jail in Equatorial Guinea.
In a meeting with Mann in 2003, they discussed the viability of renovating two civilian helicopters.
Mann told him they were to be used for a mining operation in Sudan.
And Thatcher revealed that he had transferred $275,000 (£145,000) to an aviation company to pay for the charter of the helicopters.
But throughout his evidence, Thatcher insisted he had nothing to do with any coup plot.
Last month, he admitted breaking South African anti-mercenary laws by agreeing to finance the helicopters.
Thatcher admits knowing Simon Mann, in prison in Zimbabwe
He was given a suspended jail term and fine after agreeing a plea bargain to help investigators.
As he left the courtroom, there was a lot of pushing and shoving in the throng of journalists waiting for him outside.
But Thatcher looked relieved, claiming it was a mystery to him as to why he had been called to answer these questions when the court case in Equatorial Guinea had already finished.
Responding to a question about rumours of his relocating to Switzerland or the US, Thatcher said that this was pure speculation, and he was looking at other residences in Cape Town.
Thatcher still has his admirers in South Africa.
As he worked his way through the crowd of journalists, he was approached by a homeless man who tried to show him his social security paperwork.
But Thatcher clearly was not ready for another interrogation, and he sped off in a waiting car.