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Well, Grandad was a postman for 26 years, some of those through WW2, so it could be part of the reason. He didn't go to war because the post was a reserved occupation, and he joined the Home Guard instead. However, Mum and her sister say that's a laugh, as he hardly ever went to meetings. Yet I thought he would have been kicked out if he didn't.
Do you think there was more to Grandad than meets the eye (something secret? He was always into puzzles and maps), or could he just have been a particularly good and dedicated postman?