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."
More top news
A fertility app is to be given free to one million Brazilian women in a bid to halt the spread of the Zika virus.
A woman who had a face transplant after a neighbour's chimpanzee ripped her face off is in hospital as her body is rejecting the tissue.
Trinity Mirror's new national daily will publish its final edition on Friday 6 May.