From The Sunday Times

    A source with knowledge of the police investigation said that Abedi is believed to have accessed videos online containing information about how to construct various devices, including those using TATP. Abedi downloaded material from a range of online sources, including the dark web, and the YouTube information was one part of a wider online picture, it is understood.

    After the Manchester attacks a 22-minute video on YouTube and Facebook emerged, called "Jihadi ideas for lone lions". It provided instructions on how to make the type of explosive used by Abedi.

    The video, produced by Ibn Taymiyyah, a Gaza-based group that supports Isis, showed a chemist making the explosive from scratch using items such as a funnel and coffee filter. "The filling can be used in closed places like restaurants and buses," the video says. "After the explosion, it's better to directly enter the place and eliminate those who are still alive, Inshallah." It has been taken down.