The Queen has appointed every prime minister since Anthony Eden in 1955, but Liz Truss was the first invited to Scotland.
In a break with tradition, the new PM did not meet the Queen in London at Buckingham Palace.
Instead, the monarch held an audience with the new prime minister at Balmoral.
The Queen ascended to the throne in 1952, when Winston Churchill was prime minister. Here are images of her with all 15 leaders from her 70-year reign.
Winston Churchill 1951 – 1955
The Queen, with Prince Charles and Princess Anne, meets Sir Winston Churchill in 1953
Anthony Eden 1955 – 1957
The Queen shakes hands with Sir Anthony Eden in 1956
Harold Macmillan 1957- 1963
Harold Macmillan, who also served as Oxford University chancellor, welcomes the Queen to the university in 1960
Alec Douglas-Home 1963 – 1964
The Queen speaks to Sir Alec Douglas-Home and Lady Home during a reception at County Hall in 1964
Harold Wilson 1964 – 1970
Harold Wilson with the Queen in 1969
Edward Heath 1970 – 1974
The Queen with Edward Heath, Richard Nixon and Pat Nixon at Chequers in 1970
Harold Wilson 1974 – 1976
The Queen is welcomed to 10 Downing Street by Harold Wilson in 1976
James Callaghan 1976 – 1979
James Callaghan meets the Queen for lunch at Windsor Castle in 1977
Margaret Thatcher 1979 – 1990
The Queen with Margaret Thatcher and Ronald Reagan at Buckingham Palace in 1984
John Major 1990 – 1997
The Queen with John Major, third left, and former prime ministers Margaret Thatcher, Harold Wilson, Edward Heath and James Callaghan in 1992
Tony Blair 1997 – 2007
The Queen pictured with Tony Blair at Buckingham Palace as she invited him to form a government in 2002
Gordon Brown 2007 – 2010
Gordon Brown meets the Queen in 2007
David Cameron 2010 – 2016
David Cameron at Buckingham Palace in 2010 as the Queen invites him to form a government
Theresa May 2016 – 2019
Theresa May visited Buckingham Palace as she became prime minister in 2016
Boris Johnson 2019 – 2022
Boris Johnson visited Buckingham Palace in 2019 to succeed Theresa May
Liz Truss 2022 onwards
Liz Truss became the 15th prime minister to be appointed by the Queen as she took over from Boris Johnson
