The deputy director-general of MI5 has been named as the new head of GCHQ.
Jeremy Fleming will succeed Robert Hannigan as director of the agency often referred to as Britain's listening post.
His appointment was announced on Monday by Foreign Secretary Boris Johnson, who said he is a "dedicated public servant whose work over two decades in the intelligence services has helped to keep our country safe".
“Jeremy Fleming is a dedicated public servant whose work over two decades in the intelligence services has helped to keep our country safe.
"I congratulate Jeremy on his appointment as Director of GCHQ at an important time for the service.
"I know that he will continue the excellent work of Robert Hannigan in leading this outstanding organisation, when the skill and ingenuity of the UK intelligence community are critical to defending Britain from cyber attacks, terror plots and other activities that threaten us and our allies."
Speaking about his appointment, Mr Fleming said: "It is a great privilege to be asked to lead GCHQ as it approaches its centenary in 2019.
"The organisation has a distinguished past and an increasingly important role to play in keeping Britain safe in the digital age.
“From managing cyber risks posed by nation states to preventing terror attacks, keeping our children safe online and supporting our Armed Forces, the exceptional men and women of GCHQ operate on the new frontline of global challenges.
“I'd like to pay tribute to Robert Hannigan, who over the last few years has led GCHQ through the transformation of some of our most important national security capabilities.
"I look forward to building on his legacy and in particular, the role he has played in increasing the transparency of GCHQ's crucial work and in expanding its cyber mission through the work of the National Cyber Security Centre."