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
The Duke and Duchess of Cambridge went salmon fishing in Canadian waters on the latest leg of their royal visit to the country.
What happens when a former president holds up a current president hoping to fly home for dinner with his family?
Following a bruising televised debate with Hillary Clinton, Donald Trump's week seems to have only got worse.