Brexit risks strengthening dissident republican groups and boosting organised crime, according to the first survey of links between terrorism and crime in the UK and Ireland.

Dozens of defectors have deserted Islamic State, shattering the group’s self-proclaimed image of a “jihadist utopia”, according to a new report.

Mohammed Emwazi, the Briton identified in reports as Islamic State executioner ‘Jihadi John’, has been described as “extremely kind” and “extremely gentle” by a man who has known him since 2009.

An estimated 30 Irish citizens had travelled to fight in Syria and Iraq by the end of last month — up 15% on last year.