One of these areas was a yard near Buckingham Palace Road where staff take deliveries and which is cornered by royal offices.

It is understood that the Royal Household has now banned smoking outright after concerns were raised about smoke drifting into the buildings from outside.

Those with accommodation in the grounds, including members of the Royal family and live-in staff, will still be permitted to smoke inside their homes.

However, anyone else will have to go outside of the grounds to light up.

The ban will cover Buckingham Palace, Windsor Castle, St James’s Palace, Kensington Palace and the Palace of Holyroodhouse in Edinburgh.

Clarence House has been smoke free for years at the behest of Prince Charles, who dislikes the habit.