Sir Mark Thatcher appeared in a South African magistrates' court today charged helping finance a failed coup in Equatorial Guinea.
The two-day televised hearing will try to establish the legality of the subpoena served on Sir Mark (51), son of former British prime minister Mrs Margaret Thatcher, who has worked in South Africa as a businessman since 1995.
Defence lawyer Mr Peter Hodes said the South African government would be assisting Equatorial Guinea in an unfair trial by forcing Sir Mark, who was arrested last August, to answer questions about his alleged involvement in the coup attempt.
"What we are dealing with in Equatorial Guinea is a military tribunal or there is a good possibility that it is," Mr Hodes said.
Sir Mark maintains his innocence and has promised to cooperate with authorities.
Equatorial Guinea wants to question a number of prominent Britons about allegations that they financed a plot to overthrow President Teodoro Obiang Nguema, who has ruled Africa's third-largest oil producer for the past 25 years.
Nineteen people are on trial in Equatorial Guinea, including Mr Nick Du Toit, a South African arms dealer alleged to have led an advance team for the plot. Mr Du Toit, the only suspect facing the death penalty, has outlined in his testimony meetings with Sir Mark and others in the months before the alleged coup attempt.
Last month Mr Simon Mann, a former SAS officer accused of masterminding the failed plot, was sentenced to seven years in prison for trying to buy weapons from Zimbabwe's state arms manufacturer.
Mr Mann's 67 accused co-conspirators, arrested when their ageing Boeing 727 landed at the Harare International Airport on March 7th, received sentences of 12 to 16 months for minor immigration and aviation violations.
AP