The Queen's Guards have been removed from the street and are now protecting Britain's royals behind security gates over concerns that they could be targeted in "lone wolf" attacks.
The guards, famous for their fur hats and popular with tourists visiting the royal palaces, are now behind gates at Clarence House, St James's Palace, Windsor Castle and Horse Guards Parade.
According to The Mail on Sunday, in some cases the guards are even accompanied by armed police.
The last time sentries were withdrawn from public streets was in the 1980s, during the IRA's bombing campaign.
Retired officer Major Iain Dalzel-Job of the Scots Guards told The Mail on Sunday it was a "big shame".
He said: "The reason people know we're around is because they can see us. But I suppose the changes are necessary as there is a significant threat."
Scotland Yard and Buckingham Palace declined to comment and said they did not discuss security arrangements.
More visitors to Buckingham Palace needed to help Queen pay bills
Prince Charles to turn Buckingham Palace into a hotel museum?