The new head of MI5 is the man who led the investigation into an attempted assassination of a Soviet double agent on UK soil.
Ken McCallum, a service veteran with 25 years experience, will take over in April. He replaces Sir Andrew Parker who has led MI5 since 2013.
McCallum spent the first decade of his career focused on Northern Ireland before being assigned to the fight against Islamist extremism.
He was in charge of all counter-terrorism investigations during the 2012 London Olympics, MI5 said.
Then, after former Russian double agent Sergei Skripal and his daughter Yulia were found poisoned with Soviet-developed nerve agent novichok in 2018, he led the agency’s response to the attempted murder.
MI5 said one of McCallum’s top priorities was enabling MI5 to seize the fast-moving opportunities provided by technology, including machine learning.
He said: "MI5's purpose is hugely motivating.
"Our people - with our partners - strive to keep the country safe, and they always want to go the extra mile.
"Having devoted my working life to that team effort, it is a huge privilege now to be asked to lead it as director general."
Sir Andrew said: "Ken will make an outstanding director general.
"He's the right person to take MI5 forward and is already leading work to shape the future of MI5.
"He brings a wealth of leadership and national security expertise to the role, which is all the more important today as MI5 and the country deals with the impacts of the coronavirus pandemic."
McCallum has been deputy director general of MI5 since April 2017, with responsibility for all of MI5's operational and investigative work.
Mr McCallum led the Security Service's strategic response to the 2017 terrorist attacks.
In 2012 he took charge of all counter terrorism investigations and risk management in the run-up to, and during, the London Olympics.
Mr McCallum began his career in MI5 with 10 years focused on Northern Ireland-related terrorism.
He grew up in Glasgow and holds a maths degree from Glasgow University.
MI5 said his out-of-work life is dominated by "trying to be an active father" and he enjoys mountain hiking.
