Mr Mark Thatcher must submit to questioning in a South African court this week over charges he was involved in a foiled coup plot in oil-rich Equatorial Guinea, the Cape High Court ruled today.
A full bench of the High Court upheld a subpoena forcing him to answer questions set by Equatorial Guinea investigators. The questioning is set for Friday.
The 51-year-old son of former British prime minister Mrs Margaret Thatcher had sought to have the subpoena set aside, saying the questions would infringe on his right to silence and may impact on his trial in South Africa, and in Equatorial Guinea should he later be extradited.
Judge Deon van Zyl rejected this argument, saying South African Justice Minister Brigitte Mabandla was within her rights to seek Mr Thatcher's responses to the Equatorial Guinea questions.
"She was perfectly entitled to accept the existing scenario as an issue of foreign policy and co-operative relations between South Africa and Equatorial Guinea," Judge van Zyl said, adding that Mr Thatcher's rights would not be compromised.
"At no stage have such rights been violated or even threatened," he said.
Mr Thatcher was already due to appear in a regional court tomorrow on South African charges that he helped finance a plot to oust long-time Equatorial Guinea leader Mr Teodoro Obiang Nguema Mbasogo. Mr Thatcher denies the charges.
The West African country, the continent's third biggest oil producer, says it intends to extradite him to face similar charges as 14 other suspected foreign mercenaries currently on trial in Malabo.