Hi
I am not great with traffic matters but this is what Sec 89 of the Road Traffic Act 1984 states:
89 Speeding offences generally..
(1)A person who drives a motor vehicle on a road at a speed exceeding a limit imposed by or under any enactment to which this section applies shall be guilty of an offence..
(2)A person prosecuted for such an offence shall not be liable to be convicted solely on the evidence of one witness to the effect that, in the opinion of the witness, the person prosecuted was driving the vehicle at a speed exceeding a specified limit..
(3)The enactments to which this section applies are—.
(a)any enactment contained in this Act except section 17(2);.
(b)section 2 of the M1Parks Regulation (Amendment) Act 1926; and.
(c)any enactment not contained in this Act, but passed after 1st September 1960, whether before or after the passing of this Act..
(4)If a person who employs other persons to drive motor vehicles on roads publishes or issues any time-table or schedule, or gives any directions, under which any journey, or any stage or part of any journey, is to be completed within some specified time, and it is not practicable in the circumstances of the case for that journey (or that stage or part of it) to be completed in the specified time without the commission of such an offence as is mentioned in subsection (1) above, the publication or issue of the time-table or schedule, or the giving of the directions, may be produced as prima facie evidence that the employer procured or (as the case may be) incited the persons employed by him to drive the vehicles to commit such an offence.