The Motorways Traffic (Speed Limit) Regulations 1974 No. 502

3.  No person shall drive a motor vehicle on a motorway at a speed exceeding 70 miles per hour:

Provided that this Regulation shall not apply to the driving of a motor vehicle—

(a) on any of the lengths of motorway referred to in Regulation 4 or 5 below; or

(b) on any other length of motorway on which there is for the time being a restriction imposed under section 13 of the said Act of 1967 on the driving of a motor vehicle in excess of a maximum speed which is less than 70 miles per hour.