The British military has been training interrogators in techniques that include threats, sensory deprivation and enforced nakedness in an apparent breach of the Geneva conventions. Training materials drawn up secretly in recent years tell interrogators they should aim to provoke humiliation, insecurity, disorientation, exhaustion, anxiety and fear in the prisoners they are questioning, and suggest ways in which this can be achieved. A manual prepared in April 2008 suggests that Cpers" - captured personnel - be kept in conditions of physical discomfort and intimidated. Sensory deprivation is lawful, it adds, if there are "valid operational reasons". It also urges enforced nakedness. More recent training material says blindfolds, earmuffs and plastic handcuffs are essential equipment for military interrogators, and says that while prisoners should be allowed to sleep or rest for eight hours in each 24, they need be permitted only four hours unbroken sleep. It also suggests that interrogators tell prisoners they will be held incommunicado unless they answer questions. The 1949 Geneva conventions prohibit any "physical or moral coercion", in particular any coercion employed to obtain information. All the British classified training material was produced after the death of Baha Mousa, the Iraqi hotel receptionist tortured to death by British troops in Basra in September 2003.