Possible Clues:

• Looking back, explains radiation to Anthony, Joseph and Edward as if it happened before
• Old leader admits positive word from Berlin gives you familiar feeling
• Illusion of familiarity
• Feeling one's experienced a situation before
• Experience of thinking that situation had occurred before
• A lesser figure in Jude the Obscure - have you read this somewhere before?
• "This seems familiar" feeling
• Uncanny experience that makes Dave and June not half confused
• Cuckoo due to circle island without a sense of familiarity
• It may accompany a new experience