David Cameron gave MI5 agents ‘licence to kill’ in secret letter saying they should not be prosecuted for crimes, tribunal hears

The authorisation gave spooks James Bond-style clearance to murder and torture threats to national security free from any possible criminal repercussions.

The policy, known in the industry as the ‘third direction’ and in existence since the early 1990s, was so secret that when a retired judge was introduced to oversee the policy in 2012, he was instructed by the then PM not to comment on its legality.