Police disabled a car bomb containing gas cylinders in the heart of central London on Friday morning, close to the world's largest Apple Store on Regent Street.
Police officers carried out a controlled explosion after reports of a suspicious vehicle parked in nearby Haymarket at around 2am. Haymarket is near the Regent Street shopping area, where Apple's main store is based.
A police source said the bomb was a "big device" and posed a real and substantial threat to the surrounding area.
The area is likely to remain closed for some time, with severe travel disruption predicted. Piccadilly Circus Tube station is closed and trains are not stopping, while local bus services are being diverted.