He worked for many years as a foreign affairs and defense specialist with the United Kingdom government.
The contacts he made in government later enabled him, as an author, to navigate and gain access, via the Cabinet Office, to classified intelligence services archives.
He interviewed the descendants of people who featured in Reilly's story and scrutinized over 2,000 closed or unpublished documents in 14 different countries.
He was only the fifth historian to be given special permission under the 1992 “Waldegrave Initiative” by the Cabinet Office to examine closed MI5 documents that will never be released.
He was historical consultant for the Channel Five Jack The Ripper - Tabloid Myth documentary (2009; in the popular Revealed strand).