If Library staff are a bit thin on the ground today, it’s because some have gone on a summer visit to Kew:
http://www.nationalarchives.gov.uk/
and if that doesn’t grab you, perhaps this section will:
http://www.nationalarchives.gov.uk/spies/ciphers/default.htm
or if even that is too real, maybe:
Tags: aliens, ciphers, Codes, Kew, library visits, National Archives, UFOs