• 
  Max Hastings

  Himself - Writer & Historian
• 
  Rupert Penry-Jones

  Himself - Voiceover (voice)
• 
  Robert Wade

  Himself - James Bond Screenwriter
• 
  Don Webb

  Himself - Research Volunteer, Porton Down
• 
  Harry Ferguson

  Himself - Author; Former MI6 Officer
• 
  Melissa Boyle Mahle

  Herself - Former CIA Operative (as Melissa Mahle)
• 
  Jonna Mendez

  Herself - Former CIA Officer
• 
  Valerie Plame

  Herself - Former CIA Operative (as Valerie Plame)

• 
  Annie Machon

  Herself - Former MI5 Officer
• 
  Jean Barker

  Herself - Bletchley Park Veteran (as Baroness Trumpington)
• 
  Tony Mendez

  Himself - Former CIA Officer
• 
  Bob Baer

  Himself - Former CIA Officer
• 
  Henry L. Schatz

  Himself - Former US Diplomat, Tehran (as Lee Schatz)
• 
  Kevin Macnish

  Himself - Former GCHQ Analyst
• 
  Bernd Roth

  Himself - Former Stasi Officer