Neil Shastri-Hurst: Britain must stop turning a blind eye to the threat from China

China's proposed embassy is about far more than one building in London; it is a test of whether Britain has fully grasped the nature of the challenge before us. We should be confident enough to engage with China but clear-eyed enough to recognise when our security, sovereignty, and the promise we made to Hongkongers regarding safe refuge without intimidation, are at risk.