Police evacuated Parliament Square and shut Whitehall after a “suspicious package” was found in Westminster.
Scotland Yard cordoned off Whitehall between Trafalgar Square and Parliament Square as specialist officers investigated.
Officers were called to reports of a suspicious package in King Charles Street, near the junction with Parliament Street, at 5.20pm.
Exits from Westminster Underground station onto Whitehall, home to several government buildings, were closed.
It came as protesters prepared to descend on Westminster as part of the November 5 Million Mask March.
Roads reopened after police declared the area safe at 6.40pm.
