A BMW X5 was stolen on Monday morning after its owner left the car to get warm on its drive.
Police believe an opportunistic thief took the car from Hill Rise, Cuffley, at around 7.40am.
Just an hour later another car was pinched in the village, again off the driveway of its owner in Tolmers Road.
The silver Smart car was also left with the engine running.
Sgt Nat Landau said: “Don’t make it easy for thieves – never leave your vehicle unattended with the keys easily available.
“Your back may be turned for just a few moments, but it only takes seconds for them to drive away with your car.”
Witnesses to either incident should call police on 0845 33 00 222.
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