Coombe v DPP [2006] EWHC 3263 (Admin), [2006] All ER (D) 296 (Dec):
Under s 85 of the Road Traffic Regulation Act 1984, for a motorist to be convicted of speeding, it is a requirement that the relevant road signs could reasonably be expected to indicate the limit to approaching drivers in sufficient time for them to reduce from a previous lawful speed to a speed within the new limit.