(1)It is an offence for a person to drive a heavy goods vehicle of any class on a road if he is not licensed under this Part of this Act to drive a heavy goods vehicle of that class.
(2)It is an offence for a person to cause or permit another person to drive a heavy goods vehicle of any class on a road if that other person is not so licensed to drive a heavy goods vehicle of that class.
(3)Nothing in subsection (1) or (2) above makes it unlawful—
(a)for a person who is not so licensed to act, or
(b)for a person to cause or permit such a person to act,
as steersman of a heavy goods vehicle (being a vehicle on which a speed limit of five miles per hour or less is imposed by or under section 86 of the Road Traffic Regulation Act 1984) [1984 c. 27.] under the orders of another person engaged in the driving of the vehicle who is licensed in that behalf in accordance with the requirements of Part III of this Act and this section.
(4)Neither subsection (1) nor subsection (2) above applies to the driving of, or the causing or permitting of a person to drive, a vehicle in any case where—
(a)the excise duty in respect of the vehicle under the [1971 c. 10.] Vehicles (Excise) Act 1971 is chargeable at the rate applicable to vehicles specified in paragraph 2(1) of Schedule 3 to that Act, and
(b)the vehicle is being driven for one of the purposes for which it must solely be used if the duty is to remain chargeable at that rate.