The best smartphone security doesn't help when you are forced to unlock your phone.
Also, keep in mind, remote wiping your phone after the police take it is evidence tampering. In the US, that alone can get you imprisoned.
With that said, I don't understand how he could not have expected that when visiting China.
He was employed by the British consulate in Hong Kong. Generally it's not a good idea for countries to torture people working for foreign consulates given that it's sure to spark huge diplomatic crises. The level of physical abuse forced on him is despicable, hopefully the EU will have the guts to impose strict economic sanctions on China to deter the Chinese government from taking insane actions like this again.