With General Sir Nick Carter set to step down as Chief of the Defence Staff – the head of the Armed Forces – the Prime Minister has started interviewing candidates to become his new military leader.
Gen Carter had been expected to retire in June, but was asked by Boris Johnson to stay on in post until late 2021.
But who exactly is in the running for the job?
Admiral Sir Tony Radakin – First Sea Lord
The head of the Royal Navy, the First Sea Lord has served in a number of conflict zones – including the Falklands and Iraq.
Sir Tony has also commanded in a number of roles and played a part in negotiating the recent landmark Aukus deal between the US, UK and Australia.
The Prime Minister is said to have been pleased by the decision to appoint James Bond actor Daniel Craig as an honorary commander in the Royal Navy.
If selected, Adm Sir Tony Radakin would be the first naval officer appointed Chief of the Defence Staff since Admiral Sir Michael Boyce, who was in post between 2001 and 2003.
General Sir Mark Carleton-Smith – Chief of the General Staff
The head of the British Army, General Sir Mark Carleton-Smith, is another military service leader interviewing for the role.
He is said to have a good personal relationship with the Prime Minister, both having studied at Eton.
Militarily, he served in the Gulf and Balkans, as well as commanding 22 Special Air Service in Iraq and Afghanistan.
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He also commanded 16 Air Assault Brigade in Afghanistan and served as Commander Helmand Task Force and Commander British Forces Afghanistan.
Sir Mark also provided troops and military planners in the UK's fight against coronavirus.
However, could recent issues with the Ajax programme count against him?
Air Chief Marshal Sir Mike Wigston – Chief of the Air Staff
Completing the set of military service leaders, Air Chief Marshal Wigston is also set to be interviewed for the role.
The head of the RAF has served in Iraq and Afghanistan, including as the Director of Air Operations in Headquarters ISAF Joint Command and was awarded a CBE in 2013 for the role.
He also led a review, commissioned by the MOD, into inappropriate behaviour in the Armed Forces in April 2019.
However, he is reportedly "unlikely" to be appointed in the role.
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Vice Admiral Sir Ben Key – Commander of Joint Operations
The Prime Minister is said to have wanted three-star military officials to apply for the role.
It is reported the Defence Secretary invited three to apply, but only Vice Admiral Sir Ben Key accepted the invitation.
Having served on, and commanded, numerous Navy ships, Sir Ben also served as an advisor to the Iraqi Director Joint Staff in Baghdad and was awarded the US Bronze Star in 2006 for his service.
He was also in charge of Operation Pitting – the UK's evacuation of Kabul airport in August.
General Sir Patrick Sanders – Head of Strategic Command
General Sir Patrick Sanders is in charge the UK's military approach to the cyber domain, managing allocated joint capabilities from the Army, RAF and Navy.
Sir Patrick is also one of the leaders in establishing the UK's response to subthreshold warfare from adversaries.
He has previously served in Northern Ireland, Kosovo, Bosnia, Iraq and Afghanistan.