Security improvements totalling £850,000 have been made at Nissan's Sunderland production plant after it became the target of a criminal gang.
Thieves got into the Nissan compound at Washington by blending their van in with other vehicles at peak busy times such as shift changes.
Once on the factory site the gang used insider knowledge to help themselves from a car park filled with newly made vehicles which were parked up with the keys in the ignition.
Newcastle Crown Court heard that on January 10 three Nissan Quashqais, worth £21,000 each, were stolen from the plant.
An £18,000 Nissan Juke was taken around the same time.
Nissan got back all of the stolen vehicles but the company's policy is the vehicles affected cannot now be sold to customers.
As a result of the criminal activity Nissan spent over three quarters of a million pounds updating its security systems.
Two men have been jailed for theft and handling stolen goods.