It was June 1997 and I was standing in the crowd on Hong Kong’s waterfront in torrential rain. A sad bugle played as the flag was lowered, and the royal yacht Britannia carried the Prince of Wales out to sea – and Britain out of its last Asian colony. We all had one thought. Thank goodness that’s over. Hong Kong’s last governor, Chris Patten, left what China clearly saw as a mess on the carpet, an elected assembly under the slogan “one country, two systems”. No one expected it to last, but Britain left with a certain dignity.

So why did Britain’s foreign secretary, Jeremy Hunt, take it on himself this week to revisit the scene? He applauded Hong Kong’s recent demonstrations and warned Beijing not to crack down on the rioters. He said the Chinese regime should not use a few broken windows as “a pretext for repression”. Britain would not stand for it. He said there would be “serious consequences”.

As was glaringly obvious, Hunt’s remarks had nothing to do with Hong Kong. He was puffing up his chest and signalling virtue in his contest for Downing Street with Boris Johnson. He wanted to show himself a player who could talk big on the world stage, who could move mountains. Johnson, he implied, could only move a few London cycle lanes.

China’s ambassador in London, Liu Xiaoming, might well have let this childishness pass, but he could not resist a crushing rejoinder. He said the issue was not the freedom of Hong Kong’s citizens to protest, which has been much tolerated over recent weeks. The issue was violence and vandalism against a democratic assembly. That was a crime. London should understand that, under Britain’s much-vaunted legacy, Hong Kong’s elected government and judiciary were responsible for crime, not Beijing.

Facebook Twitter Pinterest Jeremy Hunt: ‘He was puffing up his chest and signalling virtue in his contest for Downing Street.’ Photograph: Pool/Reuters

Liu pointed out that Hong Kong had enjoyed more democratic self-government under the shadow of Beijing than it had in a century and a half of British rule. Under Britain “there was no freedom, no democracy whatever” nor the right “to have an independent judicial power”. Hunt’s “gross and unacceptable” remarks offended the guiding principles of “mutual respect and non-interference in internal affairs”, long espoused by both countries. A spokesman in Beijing went further. Britain was hypocritical. He implied that it should sort out Brexit and leave Hong Kong to mend its own windows. The Foreign Office summoned the ambassador and told him not to be so rude – or once again there would be “serious consequences”.

The 1984 and 1994 bilateral accords on Hong Kong’s future were diplomatic triumphs of post-colonial history. Compromises were reached between diametrically opposed positions. China conceded the colony half a century of democracy to 2047, largely in return for a quiet life and a useful business outlet. As a result, a partial autonomy survived in the territory even during periods of repression elsewhere in China.

Anyone who now visits Hong Kong is aware of the fragility of this settlement. The presence on Chinese soil of a measure of alien democracy and human rights hangs by a thread. Recent street protests against the brutal extradition law were impressive and, so far, successful. The weekend’s descent into violence was trivial but, to a hypersensitive Beijing, alarming. The demonstrators provocative unfurling of the old British flag played into the hands of the Chinese hard-liners.

Play Video 1:40 How Hong Kong protesters used hand signals and human chains to storm government – video explainer

The reality has always been that the 1984 deal depended on Beijing sticking to it; and that in turn will depend on how far the activists in Hong Kong push their luck. Beijing has already toppled three Hong Kong chief executives, and dares not lose effective control. The one certainty is that what happens between now and 2047 will be the outcome of a resolution of forces within China’s shifting elites, and nowhere else.

It is therefore hard to imagine a more blundering, cliched and counterproductive intervention than Hunt’s. The idea that Beijing would shift its policy one inch because someone halfway round the world was frantic to advance his career is farcical. As for Britain offering any practical aid or comfort to the street protesters, that is preposterous if not a cruel deception. What does Hunt mean by serious consequences? Will he send an aircraft carrier?

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The ritual of British ministers “raising human rights issues” with Beijing has long been a charade. The post-2008, pre-2012 Olympics talks – with London begging advice while criticising human rights abuses – was embarrassing to all concerned. The same went for David Cameron and George Osborne’s bizarre “kowtow diplomacy” in 2015, seeking funds for such vanity projects as Hinkley Point, HS2 and the “northern powerhouse”. It just gave China leverage over chunks of British infrastructure.

Hunt is currently championing hard Brexit on the basis that vast riches lie in bilateral deals “with the rest of the world”. If so, is he really going to embargo Chinese trade as a consequence of Hong Kong? He should watch out that Beijing does not return the compliment.

As Hunt walks to his Foreign Office chamber, he passes majestic paintings and sculptures celebrating the wonders that British imperial rule brought to the four corners of the Earth. It is tempting for his head to be turned by the voluptuous symbols of British power projection. It has clearly happened. Damn it, say the pictures, we used to rule the world.

Like Tony Blair, Hunt aches to blunder about the world declaring all its evils “unacceptable” and arguing “something must be done” about them. He wants his office to “punch above its weight”. Hong Kong is not his country and not his business. Britain handed it back to China two decades ago, surrendering sovereignty over it to an immeasurably greater power. Yet for people like Hunt it seems the imperial urge will never ease.

• Simon Jenkins is a Guardian columnist