Sir Mark Thatcher has accumulated a £60-million (about R720-million) fortune through his ”business” activities — but Britain’s most tenacious journalists have failed to uncover precisely what these activities entail. On one aspect, however, they agree: Thatcher’s financial career took off after his mother, Margaret Thatcher, became Britain’s prime minister in 1979 and he traded on her position to clinch various deals, mostly in the arms trade.