The UK Home Secretary, Priti Patel, announced on Monday 30 March the new Director General of MI5 would be Ken McCallum.
Mr McCallum, who will replace the retiring Sir Andrew Parker, becomes the 18th director general of MI5, which was founded in 1909.
From Combatting Terrorism in Northern Ireland to Leading Investigation Into Skripals
Mr McCallum grew up in Glasgow and obtained a degree in mathematics from the city’s university. His main hobby is mountain hiking.
Mr McCallum joined MI5 in 1995 and spent his first 10 years combating dissident Irish republican terrorism in Northern Ireland following the Good Friday Agreement.
He is believed to have played a key role in the investigation into the Omagh bombing by the Real Irish Republican Army (IRA) in 1998, which killed 29 people.
As the terrorist threat in Northern Ireland receded Mr McCallum switched to tackling the threat from Islamist extremists following the 7 July 2005 suicide bomb attacks in London, which killed 52 people.
He then took on a role in cyber security, where he worked extensively with the private sector.
In 2012 Mr McCallum was in charge of protecting London and other UK venues from terrorist threats during the 2012 Olympics.
After the Games, he was seconded to the Department for Business, Innovation and Skills, where he led on digital security.
He returned to the MI5 and spent three years as a non-executive director on the board of the Nuclear Decommissioning Authority, which was responsible for safely taking UK nuclear power stations out of action.
In 2015 he was promoted to Director General Strategy, focusing on shaping new government legislation and strengthening MI5's partnerships with MI6 and GCHQ.
Two years later he became Deputy Director General of MI5 and in that role he took charge of the investigation of the Westminster Bridge, London Bridge and Manchester Arena terror attacks and the Sergei Skripal incident in Salisbury in 2018.
He also led MI5’s increasing concentration on tackling right-wing terrorism.