Wondering about that unbelievable news story....

Following the news story about the unsuccessfull British shipment (stopped in Bulgaria) of radioactive material to the Iranian military (useful also to build a "dirty bomb"), of course a lot of questions come to mind, such as:

• how come that lorry was only caught in Bulgaria?
• how many border controls did it previously cross without being suspected?
• how many more such transports have already successfully arrived in Tehran which were never caught?
• how many more such shipments are still planned and scheduled?
• how many more European states/companies are involved in that sort of secret trading?