When should the Union flag be flown at half mast?

users have claimed that Union Flags are flying at half-mast outside

Flags At Half Mast Over London (1941)

The Union Jack flag at Whitehall is flown at half mast following the death of Queen Elizabeth II.

Are Union Flags flying at half-mast across UK? As netizens worry for Kate and Charles

EU flag sales in UK at half mast after Brexit vote

Government Buildings to Fly Union Flag All Year | NTD UK News

EU flags at half mast at the Berlaymont building following the passing of Queen Elizabeth II

Flag lowered to half-mast at Windsor Castle after Queen Elizabeth II's death

When should the flag be flown at half staff?

EU flags placed at half-mast across the European Union following the passing of Queen Elizabeth II

EU flags at half-staff in honour of UK Queen

Flag at half-mast over the UK parliament

British flag removed from EU Council building

Union flags fly at half mast in tribute to the late Duke of Edinburgh | SWNS

Evolution of The UK Flag (1198-2023)

Flags to fly at half mast until morning after Queen’s funeral

UK lowers flag to half mast in memory of Tunisian shooting victims

Kate Middleton drama: Flags at #Buckingham Palace were not recently flown at half-mast #royal #uk

Union Jacks fly at half staff at the British Embassy in W...