David Clarke opens The National Archives' own X Files to uncover the secret, official accounts behind legendary paranormal and extraordinary phenomena. From mediums employed by the police to help with psychic crime-busting to sea monster sightings reported to the Royal Navy, Britain's X-traordinary Files brings to light a range of secret documents created by military intelligence and government agencies who have investigated and even used extraordinary phenomena or powers in recent history.

Each chapter is underpinned by original, official records held at The National Archives, which throw new light on many rumours and unsolved historical mysteries, including the Angels of Mons and other legends of the Great War plus a variety of strange phenomena reported both in the sea and in the air, from phantom helicopters to the great sea serpent of the Victorian era. The final chapter scrutinises official interest in the infamous Loch Ness Monster of Scotland and the 'Beast of Bodmin'.

These accounts are supplemented with contextual material gathered from interviews and the author's own investigations, making truly eye-opening reading for anyone interested in the paranormal.