Greetings, and a warm welcome to Rootschat.
Just to clarify, internees were not criminals (these would most likely have been imprisoned). In wartime people were interned because they were citizens of a nation which was at war with Britain. This was to prevent the risk of spying, sedition, or sabotage. Innocence or guilt were irrelevant - the only criterion was nationality.
As a sidenote - "enemy aliens" could be safer (if less comfortable) when interned due to the risk of hostility and violence from an angry public.
Philip