* Jihadi John named in Washington Post
* From well-to-do London family
* Known to counterterrorism officials (Adds more details of report)
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No comment was immediately available from the University of Westminster.
The Post said counterterrorism officials in Britain detained Emwazi in 2010, fingerprinting him and searching his belongings. (Reporting by Stephen Addison; editing by Guy Faulconbridge)
