Norman Russell 
The Dorset House Affair [PDF ebook] 

Dorset House is the home of the Claygate family, and a place where diplomats love to congregate. When young Maurice Claygate and notorious spy Sophie Lenart are found shot dead, Inspector Arnold Box, investigating the murders, hears from Head of Secret Intelligence Colonel Kershaw, that there are international ramifications to the case. Together the two men pursue a ruthless thief and a stolen document across France, bringing the affair to a devastating and unexpected climax in the great palace of Louis XIV, the Sun King, at Versailles.