WITH the ratification of the Treaty of Nanking on June 26, 1843, Sir Henry Pottinger replaced Captain Elliot, the founder of Hong Kong and a ''China expert'', as British Plenipotentiary and Superintendent of Trade. Elliot, like many ''China experts'', appeared to the home government, to put the interests of China above the interests of Britain. The situation called for a firm hand. Pottinger was a man of action. In 1810, at the age of 20, he had travelled 3,720 kilometres on a secret mission for the British East India Company, through Baluchistan, Afghanistan and Persia disguised as a Tartar horse dealer, and later as a holy man. He even managed to bluff his way through a couple of religious debates. To convince a Baluchi village elder that you are a venerable Tartar Hadju, when you have a thick Belfast accent, requires a certain amount of the Blarney. They don't make Governors like him any more. His nephew, Eldred Pottinger, was expected to succeed him. Eldred was also a secret agent and a brilliant soldier. He was in Herat on a spying mission when it was attacked by the Persians and Russians. Eldred took over the defence of the city. After 10 months the Persians and Russians were forced to lift the siege. Eldred was one of the few survivors of the ignominious British retreat from Kabul when the Afghans massacred a British column of 16,000 men. The plot of the book Flashman is loosely based on his exploits. Although ''The Hero of Herat'' seemed to bear a charmed life he was no match for the Hong Kong mosquito. He died of malaria when on a visit to Hong Kong and is buried in Happy Valley.