THE wife and children of Mark Thatcher, who was arrested

in South Africa last week

on suspicion of financing a coup attempt in Equatorial Guinea, left Cape Town yesterday reportedly bound for the United States.

The 51-year-old son of Margaret Thatcher is effectively under house arrest in his home in the city until he pays a (pounds) 167,000 bond. He has denied the charges against him.

Diane, Sir Mark's wife, who is from Texas, and the couple's two children left the house yesterday evening, escorted by security personnel.

Followed on their high-speed journey by a convoy of media vehicles, the family drove straight to the international terminal at Cape Town airport, where they were whisked through to the check-in desks and away from the cameras.

Lord Bell, a family spokesman, said they were travelling to the United States, where the children were to be enrolled in school. He said the move had been planned months ago and had nothing to do with Sir Mark's arrest. However, airline staff said the only flight departing was to London.

South African police said that Sir Mark had been planning to leave the country before his arrest, having put

his home up for sale and was winding up other aspects of his life in the country.

Sir Mark, who moved to Cape Town from the United States in 1998 but frequently travelled between the two, was ordered by a South African magistrate to hand in all travel documents and air tickets.

Equatorial Guinea is trying 19 men, 14 of them foreigners, who are suspected of plotting to topple President Teodoro Obiang Nguema Mbasogo, who has led sub-Saharan Africa's third largest oil producer for decades. Prosecutors have demanded the death penalty for one of them: Nick du Toit, from South Africa.

Simon Mann, a former British special forces officer and Sir Mark's acquaintance, was convicted in Zimbabwe on Friday on weapons charges linked to the suspected coup.

Officials from Equatorial Guinea are expected this week to fly to South Africa to interview Sir Mark Thatcher about his alleged role in the plot. Philip Higgo, Sir Mark's lawyer, said his client would be willing to answer their questions.

The claim is that Sir Mark and other individuals bankrolled a group of 90 mercenaries led by Mr Mann to overthrow Mr Obiang and replace him with Severo Moto, an opposition leader currently in exile in Spain.

The names of the financiers are said to be contained on the so-called ''wonga list''.

In March, the alleged mercenaries were arrested while on the tarmac at Harare international airport awaiting the arrival of a cache of arms. Mann insists the weapons were for guarding mines in war-torn Congo. The former Scots Guardsman faces 10 years in jail. He will be sentenced on September 10.

Yesterday, as the trial of 19 accused continued in Malabo, the capital of Equatorial Guinea, the court was told of torture and forced confessions.

Gesturing with his chained hands, one of the accused, South African Jose Cardoso, told the court: ''Is it normal

for statements to be taken

as you're being taken to the torture room, to be tortured, as I was?''

One of the alleged mercenaries, a German, died in custody after what human rights campaigners claimed was a clear case of torture.

So far, only Mr du Toit has admitted there was a plot, masterminded by ''financial people''.