Both judges had previously resisted intense pressure at home to withdraw, amid dramatic political and legal changes in Hong Kong following the passing of a national security law in 2020.

They stood firm when the local court’s two serving British Supreme Court judges, Robert Reed and Patrick Hodge, pulled out in 2022. Reed said it was not possible for them to continue “without appearing to endorse an administration which has departed from values of political freedom, and freedom of expression”.

Collins and Sumption were among five remaining British judges who issued a statement at the time expressing their commitment to the court.

They said it was more important than ever “at a critical time in the history of Hong Kong” to support the appeal courts in maintaining the rule of law and reviewing acts of the executive. The two judges are right about that. So it is all the more disappointing that they have now quit.

Sumption has been an outspoken defender of the presence of British judges on the top court, writing in The Times in 2021 that calls for them to withdraw had nothing to do with judicial independence and amounted to a “political boycott”. His statement this week will be closely watched.

The judges who have departed have chosen their words carefully. They appear to have drawn a distinction between the actions of the government and those of the judiciary. Reed said: “The courts in Hong Kong continue to be internationally respected for their commitment to the rule of law.” Collins said: “I continue to have the fullest confidence in the court and the total independence of its members.”

This, at least, offers some reassurance to the city’s legal community. As will the indication that at least four of the eight remaining intend to stay.

But the pool of non-permanent judges from overseas, usually one of five judges on the bench for an appeal, has shrunk and is now almost back at the 1997 level when Hong Kong returned to China.

The foreign judges remain important to Hong Kong. They have been described by critics as providing a veneer of legitimacy. No doubt, the presence of these internationally-renowned members of the profession make it easier for the government to argue that all is well.

But the judges, with their experience and expertise, have made a valuable contribution to the court over the years. They have, at times, delivered landmark rulings upholding human rights.

The top court’s judgment in September, requiring the government to put in place a framework for recognising the rights of same-sex couples, is a recent example.

Foreign judges have served the city well over the years, seen as a symbol of Hong Kong’s continued commitment to an independent judiciary and rule of law.

But amid tensions between China and Western governments over Hong Kong’s national security agenda, the long-term future of the arrangement is in doubt. It is in the interests of Hong Kong people that it survives.

It would be helpful to know more about the reasoning behind the latest departures. They have, at least, provided a timely reminder of the need for the courts to rule freely and fairly, without pressure. The government must support the judges – even when they rule against it.

Foreign judges were famously described as the canaries in the coal mine. Now, some of them are taking flight. Those that remain must sing, by delivering strong judgments – dissenting if necessary – that demonstrate their independence and protect the city’s rights.