British officials have allowed the export to Iran of a cargo of radioactive material that experts believe could be used in a nuclear weapons programme, The Observer can reveal. The disclosure has prompted calls for an inquiry into how the international trade in such compounds is controlled. On 31 August a truck carrying 1,000kg of zirconium silicate supplied by a British firm was stopped by Bulgarian customs at the Turkish border on its way to Tehran, after travelling 2,400 kilometres (1,500 miles) from Britain, through Germany and Romania, without being stopped. Full Story