Jonathan Clayton (left), Times correspondent, explains various legal difficulties that Sir Mark Thatcher is facing this week.

"When Sir Mark Thatcher arrived at the High Court in Cape Town this morning, he looked supremely confident. He bounded out of his BMW and up the steps like a man sure that things were going his way.

"When the High Court ruled against him he looked as if he had been hit in the stomach. He went into a shocked huddle with his legal advisers, and left court an hour and a half later with a grey face. It appears to be dawning on him that he is not going to sail through this one.

"All he said as he left was that it had been a very long hearing, but that they court had reasserted his right to silence.

"To understand what happened this morning, you need to understand that there are a number of legal processes going on.

"Sir Mark has been arrested and charged with criminal offences under South Africa's strict laws against mercenary activity. He is due to appear in a South African court tomorrow to face charges of bankrolling an attempted coup in Equatorial Guinea. Probably all that will happen tomorrow is that a date will be set for his trial.

"But in the meantime, there is a separate trial going on in Equatorial Guinea itself where 19 men are accused of being the advance party for the coup attempt.

"The Equatorial Guinea prosecutors have asked the South African government to assist them as they investigate, and as part of that they have asked for and been given permission to question Sir Mark in open court about his role.

"The Equatorial Guinea prosecutors have tabled 50 questions, including Sir Mark's links with Simon Mann, his Cape Town neighbour and friend who was the coup leader, and with Nick du Toit, the South African mercenary on trial in Equatorial Guinea. They want to ask about Sir Mark's financial affairs, and about his dealings with the security company behind the coup plot.

"Sir Mark's legal team argued today that it was unfair to expect their client to incriminate himself in open court. Anything he says to the Guinean prosecutors could be used against him in his trial in South Africa.

"But the South African High Court dismissed these arguments. They said that Sir Mark was not facing extradition proceedings to Equatorial Guinea at the moment, and that the questioning session would go ahead on Friday.

"In practice, what is likely to happen is that every time he is asked an incriminating question, Sir Mark will say that he is exercising his right to silence on the advice of his lawyer. Symbolically, this will look terrible, so today is a bad result for him."

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