For Beijing, the tens of thousands of protestors choking the centre of Hong Kong are such a dangerous outrage that mainland media cannot report on them. The real outrage is this: China agreed to hold free elections in 2017, but now a Beijing-appointed committee will determine whether candidates for chief executive can be relied on to toe Beijing’s line.

On 6 September, a Chinese embassy official wrote to the Times that in 2017 there would be a one-man one-vote election in Hong Kong. He omitted to mention that Beijing has selected the committee that will approve the candidates. On 15 September, Ambassador Liu Xiaoming wrote to the Daily Telegraph attacking Lord Patten, Hong Kong’s last governor, for criticising Beijing’s arrangements for the election and for claiming that those arrangements are a denial of democracy.

It is not unusual for Beijing to declare that black is white. What is scandalous is that the Foreign Office immediately ‘welcomed’ Beijing’s ‘confirmation’ of election ‘through universal suffrage’. Whoever wrote that in Whitehall knew it to be false.

In one sense it is obvious why Beijing has laid down this gauntlet. It is true that Hong Kong, semi-autonomous since 1997, enjoys an essentially free press and freedom of speech, nor are there strictures on its annual candlelight vigils attended by huge crowds commemorating the Tiananmen killings in June 1989. But since 1997, its Chief Executives have been selected by Beijing. What Hong Kong people had been waiting for, in their orderly way, was the day in 2017 when that top job would be theirs to vote for. Now angry, they are demanding the resignation of the current Chief Executive, C.Y. Leung.

But not far beneath the surface of distortion is something far more sinister: Beijing’s fear of anything resembling democracy. This is why the Nobel Peace Prize winner Liu Xiaobo is serving an 11-year jail sentence. On 8 December 2008, Liu was arrested for helping to publish a manifesto calling for democracy. He was soon charged with ‘inciting subversion of state power’. Democracy would mean the end of the Chinese Communist Party’s authority in China proper, and there would be a similar, if smaller, blow if Hong Kongers could freely elect their next Chief Executive.

I don’t think I am being melodramatic when I fear a reprise of Tiananmen in 1989.Then, too, I saw hundreds of thousands of mostly young students who, in mid-April, began calling for an end to official corruption and for a free press. But hardline statements by Senior Leader Deng Xiaoping condemning the demonstrations as of course subversive led to loud shouts for him to leave the stage and, soon, for democracy. Within a few days of a model of the Statue of Liberty being erected in the square, on the night of 3/4 June, the army and police began killing unarmed young people and their worker allies, and clearing the square.

In Hong Kong this week, armoured personnel carriers have been spotted not far from the city centre. Can Beijing be stupid enough to use them? Or, should I say, brutal enough? Its poodles in the city are demanding that foreign forces stop causing ‘a mess’.

But there are no foreign forces. Nor, I fear, will there be any substantial foreign outcries if the People’s Liberation Army’s 8,000-strong garrison comes out of its barracks. As an American I remember with shame the first President Bush sending his national security adviser, Brent Scowcroft, to Beijing in December 1989 to tell Deng that the US president was ‘your friend for ever’.

Will David Cameron now speak out to remind Beijing of its legal obligations? He says only ‘I feel for the people of Hong Kong’ and hopes the ‘situation can be resolved’. The Prime Minister has already agreed not to see the Dalai Lama in exchange for a cap-in-hand trip to Beijing. Will his chief of staff, Edward Llewellyn, at Chris Patten’s side during the last governor’s careful steps towards limited democracy in the ex-colony, tell Mr Cameron what Britain’s obligations are, still now, after 1997? No chance.

It would seem not merely intolerable for Beijing to repeat Tiananmen; it would seem impossible. But President Xi Jinping, a great admirer of Mao, will not allow democracy in Hong Kong. When it is cornered the Chinese Communist Party always reaches for prison sentences. When those don’t work, there is violence, not tear gas, but real violence.