Speedometers and the law

Sir.
With reference to the letter from Mr. R.T. Torrance of Melksham on the subject of accuracy of speedometers, if my memory serves me correctly the law does not require any particular accuracy at, nor even any indication of, 70 m.p.h. on a motor vehicle. The Law simply requires a means of indicating that a speed of 30 m.p.h. has been reached, and that with an accuracy of 10%. The Law has never required so much as a speedometer. This, I presume. being the reason why so very, very few cars have a speedometer which reads within several m.p.h. of the true speed at anythirtg over 50-60 m.p.h.

If I am wrong, perhaps someone will bring me up to date ?

Mildenhall, Malcolm D. Powell.
[Speedometers are not required on cars built before October 1st, 1947, or on motorcycles the engine capacity of which does not exceed 100 c.c.—Ed.]