After 13 years in parliament, rising star Chris Patten had the bad luck to be one of the few Tory MPs to lose his seat in 1992. Had he been re-elected he would probably have become chancellor of the exchequer. Instead, he found himself in the wilderness. But not for long. Within months he had been appointed governor of Hong Kong, tasked with the tricky business of presiding over the transfer of the territory to communist China. It was a lucky break. Had he been chancellor, the odds are that his political career would have come to a sticky end the following September, when the pound fell out of the Exchange Rate Mechanism. Instead, it was Norman Lamont who drew the short straw.

By the time Patten arrived in Hong Kong the clock was ticking. The 99-year lease on the New Territories had just five years to run, and it had long been accepted that the entire territory would return to China in 1997. The Basic Law, agreed in 1990 by China and the UK, was intended to provide for a smooth transition. It was supposed to establish a framework which, while recognising Chinese sovereignty, would protect the basic political, judicial and economic freedoms that Hong Kong citizens had long enjoyed. ‘One country, two systems’ was the mantra.

The plan was that the governor would in due course be replaced by a chief executive appointed by Beijing. The legislative assembly would be made up partly by directly elected representatives and partly by representatives of so-called ‘functional constituencies’, comprising businessmen and other vested interests. Unsurprisingly, the directly elected were keen to stretch the democratic elastic to the limit, while the businessmen, who all had foreign passports in their back pockets, were mainly interested in cosying up to the regime in Beijing. That, broadly, seemed to be the Foreign Office line too. Patten, a decent one-nation Tory, had other ideas.

The governorship of a wealthy colony like Hong Kong was by any standards a good number. Perks included a splendid Mid-Levels mansion, a country retreat, a yacht, the use of a helicopter and a lavish entertainment budget. In Patten’s diaries we see everyone from Mother Teresa to Margaret Thatcher passing through the governor’s living room – not to mention Rupert Murdoch, anxious as ever to protect his Chinese assets. Wherever Patten goes in the world (except Beijing) he is received at the highest level. He could just have lain back and gone with the flow, but that was not his style.

Eschewing the feathered hat, the uniform and all the other flummery that goes with governing an outpost of the British empire, he plunges into a series of walkabouts, holds public meetings, looks for ways of redistributing some wealth (Hong Kong’s finances were apparently healthy) and makes no secret of his sympathy for the democrats. The Chinese communists (‘graceless, small-minded… bullying’) and the oligarchs looked on all this with increasing nervousness. It was even rumoured that one oligarch had offered the Tory party £5 million to remove him.

He had trouble from other quarters too. Various ‘old China hands’ pop up offering unsolicited advice. Notably Sir Percy Cradock, the UK’s former ambassador to Beijing, whom Patten accuses of ‘working actively to scupper what we are trying to do’. It is apparent, also, that the Foreign Office – which he accuses of ‘appeasement’ – was running a policy of its own behind his back. Ted Heath (‘a despicable old bore’) also sticks his oar in from time to time.

Finally, on 30 June 1997, the curtain falls. Prince Charles arrives on Britannia to do the honours. The leaders of China (those ‘appalling old waxworks’ as the Prince described them in a leaked extract from his diary) descend from Beijing. There is a huge firework display. Down comes the British flag. Up goes the red flag of China. The governor and his family board the royal yacht and, escorted by a flotilla of British warships, sail off into the sunset.

This is Patten’s verdict on Hong Kong’s nascent democracy movement:

They are good and brave people. We have let them and others down. We should have delivered more explicitly on what was promised and given greater protection for the values that the great majority of Hong Kong Chinese citizens believe in.

Was that realistic, given that China ultimately held all the cards? Still, no one can accuse Patten of not doing his best.