The Jensen Code is a British children's thriller series first broadcast in 1973. When Terry Connor (David Bradley), a 16-year-old visitor to an Outward Bounds Centre sets off with instructor Alex (Tony Wright) to go potholing, he is unprepared for the disturbing day he will face. When, deep underground, Terry drops his torch, Alex heads off to look for it and is gone for hours. When Alex finally returns he has no recollection of having been absent. Terry suspects something sinister is taking place – it is surely no coincidence that there is a secret Ministry of Defence establishment nearby. But just how deeply his curiosity will involve him in dangerous matters becomes clear when he learns the truth about the ‘Jensen Code’. Originally made in colour, The Jensen Code now exists only as black and white telerecordings made for overseas sales, the colour episodes having been junked many years ago