The al Qaeda-inspired 28-year-old militant who launched London Bridge attack

Police cordon is seen at the scene of a stabbing on London Bridge, in which two people were killed, in London, Britain, November 30, 2019. [Reuters]

Nine years before Usman Khan killed two people in a stabbing spree on London Bridge, he was overheard by British security services discussing how to use an al Qaeda manual he had memorised to build a pipe bomb.

It was a snippet of conversation, along with other intelligence about a plot to bomb the London Stock Exchange, that prompted British police to arrest Khan - then 19 years old - and a group of older men on Dec. 20, 2010.