Ominous new revelations from British intelligence about Al Qaeda’s nuclear aspirations: Al-Qaeda ‘was making dirty bomb’.

British officials said on Thursday Bin Laden now had gained the expertise and possibly the materials to build a crude radioactive bomb.

The government says evidence suggests that by 1999, Bin Laden’s priority was to develop a weapon of mass destruction.

He had acquired radioactive isotopes from the Taleban to do this, officials said, adding that development work on the “dirty bomb” had been going on in a nuclear laboratory in the Afghan city of Herat.

The government even has al-Qaeda training manuals which detail how to use a dirty bomb to maximum effect.

For a second opinion, the BBC showed some of the material to an expert on al-Qaeda.

“I think this is genuine,” said Dr Mustafa Alani, of the Royal United Service Institute. “It is credible. This is proof that al-Qaeda put a lot of effort into collecting information and educating other members of the organisation. It is possible to produce this sort of weapon.”

British military personnel worked with intelligence officers to gather material which was taken to Porton Down defence research centre in Wiltshire.

Their conclusion was that al-Qaeda had a small dirty bomb but probably not a full blown nuclear device.