Tom Tugendhat is Chairman of the Foreign Affairs Select Committee, and is MP for Tonbridge and Malling.

Hong Kong has changed since handover. Through the Sino-British Joint Declaration, we tried to protect the city’s unique status and defended some of its institutions – the court, the Legislative Council and the trade agreements – but left the people exposed.

Hong Kongers before 1981 were citizens of the UK and colonies, able to come to Britain any time they chose, but the prospect of handover leading to a movement of people saw the then Government change their status, ending up with what is now British Nationals (Overseas) – BNOs.This gives only a six-month stay in the UK and restricts rights. But after years of campaigning, that’s changing.

China’s actions in forcing a new Security Law on the territory, which will allow Beijing’s secret police to open on office on the island for the first time (officially), undermines the Joint Declaration, which was so carefully woven to protect the economic power of the jurisdiction and the rights of the people. That raises important questions for us.

The Declaration is a treaty lodged with the United Nations, and places duties on both sides. We have been slow in remembering ours. From six-month reports to holding the Chinese Communist Party to their promise of One Country, Two Systems, we have sometimes remained conveniently silent when other interests seemed to count more.

Now, after decades of turning a blind eye, Beijing has forced us to see the effect of the incremental erosion of rights in Hong Kong.

As British judges join Australians, Canadians and New Zealanders as non-permanent judges on the Court of Final Appeal, there is a danger that they’ll find themselves no longer simply guaranteeing the rule of law in a semi-autonomous part of China. These changes to the civil rights of Hong Kongers risk making them cover for a new, authoritarian power.

Many are already worried. They have seen their rights eroded over recent years, and taken to the streets to protest. This new law would stop them.

It will ban “any acts or activities” that endanger China’s national security, including separatism, subversion and terrorism. Charges like these are often used in mainland China to detain dissidents and other political opponents. It now seems that the era of Hong Kong’s political freedom is over, and that many could become criminals for actions that were legal until now.

Britain’s enduring duty to the city endures. After a century of rule, our responsibility goes beyond others though, in recent times, the US has been a more vocal defender of the people’s rights than the UK. This seems to be changing.

Priti Patel, who has been actively supporting Hong Kongers since her time on the Foreign Affairs Committee and perhaps before, and Dominic Raab will change the rules for BNOs living and working in the UK, if China presses ahead with the Security Law. That’s an important move.

The Foreign Office is also becoming clearer in raising concerns about the actions of the rulers in Beijing. But there is more we can – and should – do.

From calling out the abuses to offering sanctuary to those who need it – or soon will – there is an important role for us to coordinate. Hong Kongers have diaspora populations around the Pacific, particularly in Canada and Australia, and many would not wish to come to the UK, but we should welcome those British Nationals who should are eligible.

Though millions have arrived since handover in 1997, those who were there before were stripped of their rights, and these should be restored.

Britain has gone out of its way to help China – from supporting Beijing’s admission to the World Trade Organisation on favourable terms to pushing others to join the Asian Infrastructure Investment Bank, and working to help the renminbi to be traded abroad.

These weren’t purely acts of altruism, but they have set London apart as a destination for Chinese students, businesses and tourists. It’s what created the so-called Golden Era between our two countries. We were China’s partner in Europe.

In building that partnership, we turned a blind eye to intellectual property theft, spying, and even censorship in our own universities. Now Beijing’s actions are calling into question Britain’s word as an international partner. We must act.

That’s why these first steps are welcome. We must move faster in recognising the rights of the most entrepreneurial people in Asia, and speak out for those who we know so well back in the region. We should also build partnerships that can defend the rule of law worldwide.

If Global Britain is to mean anything, we must stand up for the deals we struck and the people we owe duties to. If we’re not prepared to speak up for British Nationals, why should others count on us at all?