Asked if GCHQ could guarantee it does not operate beyond UK law, Sir Iain Lobban replied: "I can give you that guarantee. I believe that to be true. We are subject to the law."
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Shouts of "we are not afraid" rang out across Barcelona as people gathered to pay tribute to those caught up in the deadly terror attacks.
Showers often confined to northwest Scotland - filtering further south at times.
A Spanish court has released photos of four suspects they are hunting over the terror attacks in Spain.