The Underground Metropolitan Line runs out to Watford. Do not confuse this with the major Watford Junction station, it is a cute cottage-building terminus in residential roads about a mile away. It does have a little cab rank out front, and is no further from the studios (which are on the old Leavesden Airfield site) than the Junction station. Baker Street station is a good place to pick up the Metropolitan Line, and the trains are the speediest on the Underground.