He was interned and shipped to Australia in the HMT "Dunera", a boat that became famous for the talent it brought to Australia and for the unpleasantness with which its human cargo was treated. They encountered a more relaxed attitude in Australia – one guard summing up the character of the 'friendly enemy aliens' and famously asking one of them to hold his rifle while he lit a cigarette. Still, they were transported to a camp in Hay, a remote town in NSW. Both on the boat trip to Australia and thence at Hay, Gruen benefited from the ubiquity of highly educated fellow inmates from musicians to philosophers of considerable standing in Europe. These people became mentors, and Miss Margaret Read (later Mrs Margaret Holmes) of the Student Christian Movement assisted Gruen and others in accessing books and other University resources for study.