The business district may be more Manhattan than the Square Mile, the malls more Las Vegas than London, and, since the inception of the new state security law, the police and security apparatus overwhelmingly mainland Chinese. But in Hong Kong, as with numerous other ex-colonies, the legal system and courts are resolutely English. It may be sweltering in the 90s, but wigs, gowns and three-piece suits remain. English law reports line walls in the grandiose colonial-era supreme court building; and the language in most cases retains the analytical precision and courtesy of the 1960s before the English system changed irreversibly in the face of a combination of EU influence, pervasive European human rights culture and a less meticulously educated cadre of lawyers.

Before 1997 the Hong Kong legal system apexed at the final colonial court of appeal in London, the Judicial Committee of the Privy Council, a body largely coextensive with the Law Lords (though with a few other co-opted judges from the UK and sometimes the Commonwealth). Understandably unhappy at this institutional extension of empire, Beijing insisted the privy Council be replaced with a local supreme court (the so-called Court of Final Appeal (CFA)). That court, however, was given from the outset the specific power to co-opt judges from the UK and elsewhere in the common law world, an arrangement that remains to this day. By convention the Law Lords (now the UK Supreme Court) supply two of their number as and when required, and a number of other English judges are also asked to serve occasionally. There was no reason for Beijing to object to a practice of this kind. It was in everyone’s interest to maintain Hong Kong as a major legal and commercial centre, with the best quality common law judges, and in any case a Chinese-controlled Hong Kong could put an end to the scheme whenever it liked.

Today there is indeed pressure to suppress this rather effective remnant of colonialism. Perhaps surprisingly, however, it is coming not from Beijing but from London. Three weeks ago Tom Tugendhat, a noticeably vocal anti-China hawk on the parliamentary foreign affairs select committee, suggested that any continued UK judicial presence in Hong Kong was unacceptable following the activation of the new Law on safeguarding National Security sponsored by Beijing. “How,” he said, referring to the co-opted judges from the UK, “can they do that, how can they defend civil rights and commercial rights if they are being violated by the very law they are sent to uphold?” Last week the Supreme Court judges took the hint. In a fairly terse message put out by their office, they said they would liaise with the government; whether they continued to serve would “depend on whether such service remains compatible with judicial independence and the rule of law”.

The co-opted judges on the CFA retain the ability to cause some wholesome embarrassment to the new ruling clique

At first sight the idea of withdrawing judicial links between the UK and Hong Kong by engineering a mass resignation looks like a welcome and dignified protest against what is clearly a devastating attack on the freedom of the people of Hong Kong. The closer one looks at the idea, however, the less attractive it becomes.

For one thing, this is getting perilously close to encouraging political involvement by the judiciary. When many of these same Supreme Court judges used their power last December to unprorogue Parliament, citing a duty to promote Parliamentary accountability as a “foundational principle of our constitution”, they were rightly criticised for judicialising the promotion of constitutional virtue. It is true that the Hong Kong national security law contains some pretty unpleasant provisions, especially those curtailing the right of protest, giving plenary powers of search to police, limiting jury trial and allowing only certain judges to hear national security cases; nevertheless, however personally repelled they may feel, there is a strong case that the judiciary, including the UK element, would be distinctly best advised to keep a discreet silence about it.

For another, if you could somehow persuade the new authoritarians in Beijing to tell you what they thought of a possible mass judicial walkout, one suspects that the answer would not be hard. Such an event would actually suit them rather well. Judges who went would have to be replaced, and despite the existence in Hong Kong of a formally independent Judicial Officers Recommendation Commission it is a racing certainty that any replacements made by the Chief Executive would consist of those who could be trusted not to rock the boat.

By contrast, in place the co-opted judges on the CFA retain the ability to cause some wholesome embarrassment to the new ruling clique. True, it would be improper for them to make their position known openly in a political minefield such as this. But with nothing to lose, at least they would be able to be trusted to interpret Hong Kong public law fairly, dispassionately and without a look over the shoulder at what Beijing’s agents in their new office in Causeway Bay might be thinking. Even with the new national security law, asides and raised eyebrows can still do much: a good deal can be made of a comment in the course of a judgment that a provision of the new law, while it must of course be applied according to its strict meaning, is an unprecendented restriction on a common law freedom that would otherwise exist. Moreover, measures like this would put Beijing in a bind. Hong Kong could hardly follow the example of countries like Zimbabwe, which when faced with senior judges who failed to do what the government told them in 2001 simply sent round thugs to threaten them with death unless they went (which they did, fast). The Hong Kong government could of course take measures to sack them or abolish their posts. But this would be an additional cause of embarrassment and create a need for explanations, which is something the government in Beijing can at present do well without.

Nor is all this simply a matter of liberty, public law and the right to protest. Listening to the news coming out of Hong Kong, it is easy to miss the fact that the ex-colony, with its resolutely mercantile ethos, depends for its prosperity on its status as a major trade and business hub. At this it remains very successful. Put bluntly, if you steer clear of politics and settle down to the serious matter of running a business and making money, then despite any number of new security laws you are still likely to be left alone to add to general prosperity.

However, this pre-eminence is by no means guaranteed. Hong Kong once might have been able to say that it was China’s only window on the outside world, but no longer: cities such as Shanghai or Shenzhen are not only highly competitive but bigger, and now almost as readily accessible. But what Hong Kong does still have is English common law, the legal system of choice (certainly over PRC law) for vast numbers of businesses worldwide. To take advantage of this, however, it crucially needs to be able to guarantee the proper application of that law. That means, among other things, courts which can be trusted not only to apply the law impartially, but to get it right. The withdrawal from its legal system of a cadre of foreign common law judges at the top of their respective professions, and their replacement by local, more trustworthy, ones would put a large dent in this reputation. This would be bad, not only for the economy of Hong Kong, but for the Hong Kongers who depend on it.

In short, as regards the foreign co-opted judges, staying in post carries benefits for Hong Kong in terms not only of freedom but of prosperity and stability. Walking away might yield an eye-catching headline or two and salve a few sensitive consciences in London. But it risks playing into the hands of Beijing, reducing Hong Kong to a provincial backwater more like Southampton than Shanghai, and in the long term making life harder for the ordinary Hong Konger. The choice should not be a hard one.