Because I enjoyed The Atrocity Archives so much, I attempted to locate a copy of Len Deighton's The IPCRESS file. The book is currently out of print, but a new print run will be coming out in July (did Stross put Deighton back on the map?).
Being the sort of fellow who can see through a brick wall if given enough time, I finally realized that Randall Garrett's "Lord Darcy" story The Ipswich Phial is an homage to Deighton's Book. The Ipswich Pial is a thaumaturgical espionage tale, with Lord Darcy, an agent of the Anglo-French Empire, attempting to track down a dangerous magical item before it falls into the hands of agents of the Slavonic Empire (a Polish autocratic kingdom). Randall Garrett's works featured many allusions and veiled references to other books, television shows, movies, and individuals both real and fictional... I just didn't have the wherewithal to spot the reference to Deighton until recently.
As luck would have it, I have tracked down a library copy of The IPCRESS File and will use the interlibrary loan service to get my grubby paws on it.
2 weeks ago