Does my son have to come back to UK to get his work permit?

My son has taught for 2 years at a kindergarten in mainland China. He had a degree but not in teaching and is currently sitting his tefel. The work permit he had issued in Shanghai has been declared invalid - the office that issued it was busted by the police.
His employer tells him he has to return to the UK for a face to face meeting at the Chinese Embassy to obtain his work permit (he has all the relevant paperwork required for except for the work permit which they are calling the red book).
Can he get the work permit from the Chinese embassy or an office acting on their behalf in Hong Kong ?