Dartford Civic Centre was evacuated on Saturday (Nov 2) after a metal detector enthusiast bought in an unexploded Second World War bomb.
Police sealed off the building for almost three hours after the man took in the shell which he had found in Otford.
A bomb disposal team was called in to destroy the device.
A British Army spokesman said: “It was a historic mortar bomb from the Second World War.
Metal detector fan takes in WWII bomb to Dartford Civic Centre
Aurelia's Metal Detecting 