A former Parachute Regiment officer once nicknamed the 'steely-eyed messenger of death', Dan Jarvis has a reputation for calm in the midst of a storm. 

The nickname does not come from his time in Britain's Special Forces – but four years into his political career when a man tried to mug him on the Tube. 

The 'drunk and aggressive' man threatened to break a bottle over his head if he did not hand over his wallet, Mr Jarvis said. 

The response 'that's not going to happen' and a brief standoff saw the would-be mugger back off, and MPs begin to refer to the former major by the new, sinister nickname. 

But Mr Jarvis's appointment as Defence Secretary could test this reputation, coming in the middle of a row over defence spending and wars in Ukraine and the Middle East. 

The appointment, rumoured in Westminster not long after John Healey's resignation on Thursday, is a logical one. 

Born in Nottingham, Mr Jarvis, 53, attended Sandhurst after his international politics degree at Aberystwyth University. He was commissioned into the Parachute Regiment in 1997. 

Over the next 14 years, he served major tours, including in the Balkans, West Africa and the Middle East. 

As a platoon commander in Kosovo in 1999, he was at Pristina Airport when General Sir Mike Jackson famously refused to confront Russian forces, telling his American superior: 'Sir, I'm not going to start World War Three for you.'

Mr Jarvis, who went on to become General Jackson's personal staff officer later described it as 'a very surreal moment in my life'.

In 2000 he was sent to Sierra Leone to help the Army learn from the capture of a group of British soldiers who were later rescued in a joint SAS-Parachute Regiment operation unofficially called Operation Certain Death.

He was then deployed to Iraq in 2003 and Afghanistan in 2005 and 2006, where he carried out some of the initial reconnaissance of Helmand Province.

As a major, he later completed a six-month tour in Afghanistan as company commander with 1 Para, part of the UK's Special Forces Support Group.

But in 2011, he quit the Army after being selected as Labour's candidate to fight the Barnsley Central by-election called after Eric Illsley was jailed for fraud during the expenses scandal.

A party member since the age of 18, his selection hinged on luck. After coming joint second in the penultimate round of voting, he only proceeded to the final vote after drawing lots.

He defeated Richard Burgon, now MP for Leeds East and secretary of the Socialist Campaign Group, before winning the by-election with 60 per cent of the vote.

Seven months later, he was appointed to Ed Miliband's front bench as a shadow culture minister, later becoming shadow youth justice and victims minister.

After Mr Miliband's resignation following the 2015 general election, Mr Jarvis's name was mentioned as a potential leader – which he ruled out, saying he wanted to put his family first.

He did not serve on Jeremy Corbyn's front bench, and in 2018 became the first directly elected mayor of the Sheffield City Region, while remaining an MP. He did not seek re-election in 2022.

In 2023 he became shadow security minister, taking the post in government in 2024. In that role, he has been responsible for protecting Britain, working with the security services to tackle foreign spies, cyber attacks and terrorism.

Once asked if he had any hobbies, Mr Jarvis said: 'I like the odd run.' 

This was an understatement. Mr Jarvis has run 16 marathons – and has completed the Marathon des Sables: a six-day, 155-mile race through the Sahara Desert.

He now takes on a Ministry of Defence facing a fight with the Treasury over funding and questions over how our Armed Forces should adapt to the changing nature of war.

It is a daunting in-tray, but Mr Jarvis is no stranger to a challenge.