Theft -- in UK law -- is the intentional taking of someone's property with the intent to deprive the owner of it permanently. That's why there's a specific off

Theft -- in UK law -- is the intentional taking of someone's property with the intent to deprive the owner of it permanently. That's why there's a specific offence of "Taking Without Owner's Consent" when you steal a car to joyride in (and crash and burn, rather than sell on): otherwise it's too easy to claim you only "borrowed" the car and intended to give it back, at which point it's not a crime any more.