Interrogation reports and photographs are among secret MI5 files about World War One spies being made available online for the first time.

Among the spies detailed are Swallows and Amazons author Arthur Ransome and Dutch spy Mata Hari, who was executed for spying for the Germans

More than 150 files are being made available in the digitised release.

It is part of a series by the National Archives to mark the centenary of World War One.