Inside Al Qaeda : how I infiltrated the world's deadliest terrorist organization

In October 2002 Mohamed Sifaoui met a contemporary from his school days in Algeria quite by chance.

Since the 80s, Sifaoui had become a journalist and committed opponent of Islamic fundamentalism.

His former classmate, Karim Bourti, had joined an active al-Qaeda cell in Paris.Improvising on the spot, the journalist set about convincing Bourti that he too was a follower of Bin Laden and could help with propoganda.

The astonishing result of his subterfuge was that he slowly gained the complete confidence of the cell and spent three months inside the organization.

The ultimate sign that he had gained the trust of his new associates was an invitation to visit London, the nerve centre of al-Qaeda in Europe.Mohamed Sifaoui's book is the diary of his time under cover, much of it at great personal risk, since he used a false address and frequently carried a hidden camera.

Here, for the first time, we can eavesdrop on members of al-Qaeda speaking with shocking frankness about how they raise funds, select "legitimate targets" and plan their operations.