An island that has high-speed railway connections to Europe is not exactly isolated from the world, not to mention it's ferry connections with multiple neighboring countries in mainland Europe.
Additionally, Great Britain has about 3 times the population of Taiwan, and it's urban centers have between 5 and 7x the population of Taiwan's largest urban centers.
Sure, but all the points of entry to Britain have border controls. If the government ordered the channel tunnel to stop, it would stop. It's not like France, where there are innumerable border crossing points.
Of course a total closure would be a last resort, because that would cut off imports of things like fresh fruit, but it's been possible to get 20-minute pinprick blood tests since April (admittedly with lower accuracy than PCR tests) - the government simply decided measures like testing everyone at the border and enforcing mandatory self-isolation were not priorities.
> If the government ordered the channel tunnel to stop, it would stop. [...] Of course a total closure would be a last resort, because that would cut off imports of things like fresh fruit
As demonstrated by the recent French closure:
> French President Emmanuel Macron went further Sunday, with France barring UK travelers and shutting down the Eurotunnel crossing for at least 48 hours, meaning thousands of trucks carrying goods to the continent will not be able to cross the English Channel.
