Hong Kong has long been at the centre of a tussle between mainland China and the outside world - certainly since the British took it as a colony in 1842.

That heralded more than a century of "shame" for the Chinese - but in 1997 the British handed Hong Kong back to China with internationally agreed conditions. The so-called "one country, two systems" principle was meant to last until 2047, but in recent years Beijing has tightened its control over Hong Kong.

Major pro-democracy demonstrations in 2019 were quashed and, in 2020, the authorities introduced a controversial and wide-ranging National Security Law to Hong Kong.

Over recent weeks pro-democracy campaigners have been locked up, troublesome journalists have been censured or fired from their jobs, teachers have been told they will have to explain the benefits of the National Security Law to their pupils. Some argue that this is the end of Hong Kong.

So why is Beijing and its supporters in the Hong Kong legislature taking this action now, and where might it end?

Joining David Aaronovitch on this week's programme:

Hugh Davies, a former diplomat who negotiated the return of Hong Kong

Mary Hui, journalist for Quartz

Yuen Chan, Senior Lecturer, City University of London

Charles Parton, Senior Associate Fellow at Royal United Services Institute

Producers: John Murphy, Sally Abrahams, Kirsteen Knight