This tradition changed in 1997 , following the death of Diana , Princess of Wales , when the tabloid press reported alleged public outrage because the palace did not fly a flag at half mast . The Queen was at Balmoral Castle at the time , so there was no flag flying . In response to this display of public opinion , the Queen ordered a break with protocol and the Union Flag was flown at half mast over the Palace on the day of Diana 's funeral . Since Diana 's death , the Union Flag flies from the Palace when the Queen is not in residence , and has flown at half mast upon the deaths of members of the Royal Family , and other times of national mourning such as following the terrorist bombings in London in 2005 , the deaths of Gerald Ford and Margaret Thatcher , and the terrorist attacks in Christchurch in 2019
terrorist bombings in London
7 July 2005 London bombings
Flags at Buckingham Palace