British authorities discovered a package containing "several kilos of uranium" at Heathrow airport. The uranium was not sufficiently pure to be used in a thermonuclear bomb, but it could be used a a dirty bomb with equally devastating results.
From The Sun:
Former commander of the UK's nuclear defence regiment Hamish De Bretton-Gordon said: "For uranium to turn up on a commercial airliner from Pakistan to an Iranian address in the UK is very suspect."
A former army chief has claimed the deadly shipment could have been used for a Litvinenko-style assassination plot.
Officials believe they have prevented any immediate threat to the public. They are being assisted by security services as they investigate the suspected plot.