Last month 16 people were arrested on accusations of planning or attempting to travel to the Syria or returning from its battlefields and training camps.
The soaring arrest figures - which compare with just 24 Syria-related terror arrests in 2013 - are evidence of an increased focus on the terror threat posed by a number of young Britons gaining paramilitary training and battlefield experience overseas.
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The royal couple have been in the US to mark the 300th anniversary of the foundings of New Orleans and San Antonio.
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