IN SEPTEMBER 2021, Boris Johnson had a cabinet reshuffle where he installed a Deputy Prime Minister - a role that has not been used for a number of years.

       So who is the Prime Minister's second in command?

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       Boris Johnson has worked as Prime Minister without having a deputy Credit: PA:Press Association/PA Images Who is the Deputy Prime Minister of the UK?

       Dominic Raab is the current Deputy Prime Minister - a job he holds alongside being Justice Secretary and Lord Chancellor.

       The role of Deputy Prime Minister is to effectively be the postholder and the go-to person whenever the Prime Minister is absent from carrying out their duties.

       David Cameron was the last Prime Minister to have a Deputy.

       His appointment of the then-Liberal Democrat leader Nick Clegg from 2010-2015 worked to cement the coalition partnership.

       Of the nine deputy PMs, only Clement Attlee and Anthony Eden have ever gone on to become Prime Minister.

       Usually the office holder will have a separate ministerial office to carry out at the same time.

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       The role does hold similarities with First Secretary of State.

       Under Theresa May this office was held first by Damian Green, before the de facto deputy PM responsibility was carried out by David Lidington.

       When has the Deputy Prime Minister stepped in for Boris Johnson?

       Raab has some experience in deputising for the Prime Minister.

       On April 5, 2020, Boris Johnson was admitted to hospital for 10 days after testing positive for coronavirus.

       Raab was asked to stand-in and replace him for any necessary duties during the Prime Minister's absence.

       It was described as a "precautionary step" taken on the advice of his doctor.

       However, on Monday, April 6, the PM was transferred to intensive care after his symptoms worsened.

       The Prime Minister remained in charge of the government, but Raab led the coronavirus press briefings.

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       Dominic Raab would be expected to stand in if Boris Johnson became incapacitated Credit: Getty Images - Getty Who has held the office?

       Only a few people have actually been formally appointed deputy prime minister.

       Ministers are appointed by the monarch, on the advice of the prime minister.

       Clement Attlee (1942-1945) Herbert Morrison (1945-1951) Anthony Eden (1951-1955) Rab Butler (1962-1963) William Whitelaw (1979-1988) Geoffrey Howe (1989-1990) Michael Heseltine (1995-1997) John Prescott (1997-2007) Nick Clegg (2010-2015) Dominic Raab (2021-present)