In England, Wales and Northern Ireland, taking without owner's consent (TWOC), also referred to as unauthorised taking of a motor vehicle (UTMV), describes any unauthorised use of a car or other conveyance that does not constitute theft. A similar offence, known as taking and driving away, exists in Scotland.

In police slang usage, twoc became a verb, with twocking and twockers (also spelled twoccing and twoccers) used respectively to describe car theft and those who perpetrate it: these usages subsequently filtered into general British slang.

Any unauthorised taking of a car is likely to cause distress and can cause significant inconvenience to the owner and his or her family, so this is an offence covering an everyday crime, yet one that often involves genuine emotions of personal invasion. Nevertheless, it is a summary offence defined under section 12(1) of the Theft Act 1968:

a person shall be guilty of an offence if, without having the consent of the owner or other lawful authority, he takes any conveyance for his own or another's use, or knowing that any conveyance has been taken without such authority, drives it or allows himself to be carried in or on it.

Adopting the standard section 1 definition of theft would require a dishonest appropriation of the conveyance with the intention of permanently depriving the owner. There will therefore be little difficulty in prosecuting as theft situations where the stolen car is later sold (sometimes through a process of 'ringing' i.e. its identity is changed and forged documents of title produced) or broken for spare parts, because the evidence of an intent permanently to deprive is clear. But the twoccing situation usually describes joyriding where all that is intended is an unauthorised use for a short period of time. Alternatively, it covers situations where a vehicle is taken for the purposes of another offence, e.g. it is to be used to escape after a bank robbery and then abandoned. This offence is an alternative verdict under section 12(4) which provides:

If on the trial of an indictment for theft the jury are not satisfied that the accused committed theft, but it is proved that the accused committed an offence under subsection (1), the jury may find him guilty of the offence under subsection (1).

There must be some positive movement of the vehicle. Simply rolling it forwards or backwards a few metres is not sufficient (if someone parks their car so close to yours that they make it impossible to drive your vehicle, it is permissible to move their vehicle a few feet to extricate yours) but, equally, it is not necessary that the engine be started. Releasing the brake and allowing the vehicle to run down a hill would be sufficient, as would driving the vehicle for a short distance. The taking may also be a material unauthorised use. For example, if a person hires a car to drive from London to Birmingham, but actually drives it to Liverpool, that will be a taking. The conveyance need not have anyone in it at the time of the taking; merely being a conveyance is sufficient.

To be a conveyance, the vehicle must have been constructed or adapted to carry a driver (and others, depending on the design) whether by land, water or air (so it includes hovercraft, boats and aircraft in addition to motorised land vehicles). Pedal cycles are excluded from section 12(1), but are covered by section 12(5) with reduced penalties, except for one constructed or adapted only for use under the control of a person not carried in or on it.