He will be succeeded by Mark Sedwill who is currently the Permanent Secretary at the Home Office. Philip Rutnam will in turn move from the Department for Transport to become the new Permanent Secretary at the Home Office.
Commenting on Sir Mark’s retirement the Prime Minister said: "I would like to thank Mark Lyall Grant for his long years of public service, in the Foreign and Commonwealth Office, at the United Nations and also in particular for his work since 2015 as National Security Adviser. Mark has made a huge contribution and I wish him every success for the future."
The Prime Minister added: "Mark Sedwill’s experience means that he is ideally qualified to take up the critically important role of National Security Adviser. As well as his recent time in the Home Office, he has served in both Afghanistan and Pakistan and has wide-ranging experience of foreign and security policy issues."
The Home Secretary said: "I would like to thank Mark Sedwill for his distinguished tenure as Permanent Secretary of the Home Office. He has worked hard to achieve our mission to cut crime, prevent terrorism, control immigration and protect the vulnerable. His dedicated public service has helped keep our citizens safe and our country secure. I know he will continue that mission in his new role.
"And I am delighted to announce Philip Rutnam’s appointment as Permanent Secretary at the Home Office. Philip brings a wealth of leadership and delivery experience, including working on major projects and addressing the long term needs of the UK. I look forward to working with him when he takes up his new role."
Sir Jeremy Heywood, Cabinet Secretary, echoed the comments from the Prime Minister and Home Secretary, paying tribute to Sir Mark’s time as National Security Adviser, and welcoming Mark Sedwill and Philip Rutnam to their roles: "Mark Lyall Grant’s work over recent years, in the Cabinet Office and before that the UN, has been immensely important in promoting the UK’s national interests and keeping this country secure. He has served with great distinction two Prime Ministers and the National Security Council, providing strong leadership to the whole national security team. I thank him for his service and wish him all the very best for the future.
"I congratulate Mark Sedwill and Philip Rutnam on their new roles, and look forward to working closely with them. They are both experienced Permanent Secretaries with a strong track record of leadership and achievement."
A Civil Service Commission-led competition has been launched today to find a successor to Philip Rutnam.
Jonathan Moor, Director General for Resources and Strategy at the Department for Transport, will be acting Permanent Secretary at the Department of Transport from 3 April, until a successor is in post.
Sir Mark Lyall Grant will retire from the Civil Service and his role as National Security Adviser on 13 April 2017.