GCHQ top boss Robert Hannigan has stepped down citing personal reasons, the surveillance agency has announced.
Hannigan became GCHQ director in 2014. Prior to this, he was director general of defence and intelligence at the Foreign Office.
In his resignation letter to foreign secretary Boris Johnson, he wrote that his public service roles "demanded a great deal of my ever patient and understanding family" and that "now is the right time for a change in direction".
He wrote: "After a good deal of thought I have decided that this is the right time to move on and to allow someone else to lead GCHQ through its next phase.
"I am, like you, a great enthusiast for our history and I think it is right that a new director should be firmly embedded by our centenary in 2019. I am very committed to GCHQ’s future and will of course be happy to stay in post until you have been able to appoint a successor."