CNN say police and secrity sources confirm this.
They say the vehicle was originally illegally parked at/near Traflagar Square and was towed to this location.
It looks to me, as I speculated earlier in the thread, that someone was getting assets into position last night, for an attack over the weekend.
just received this email from CNNBreaking News:
Police and security sources say they found bomb components in a second car in central London hours after deactivating a device in the city’s entertainment district