This makes for interesting reading
Cycling and the law - Bikehub - http://www.bikehub.co.uk
Confusing or what !!!
Almost as bad as which ebikes are legal
Here is the section on speeding
SPEED LIMITS DO NOT APPLY TO CYCLISTS
Possessing and propelling a vehicle equipped with an engine confers more responsibilities in law but not any greater rights. Many commenters to newspapers and online forums complain that cyclists travel too slowly and impede the progress of motorists. These commenters may be surprised to learn that cyclists share no legal obligation to adhere to speed limits. Speed limits on motor vehicles were introduced in 1903 in order to protect members of the public from the harm that can be done by excessive speed made possible by engines. The speed limit in 1903 was set at 20mph; this limit was routinely breached by early motorists. In 1934 the speed limit in towns was set at 30mph.
Not then and not since have any laws been enacted to make cyclists adhere to the speeding regulations brought in for motorised vehicles.
Rule 124 of the currently in force Highway Code states speed limits on a tabulated panel, but there is no row that applies to bicycles.
The Road Traffic Regulation Act 1984 states:
“It shall not be lawful for a person to drive a motor vehicle on a restricted road at a speed exceeding 30 miles per hour.” (RTRA 81.1)
And
“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.” (RTRA 89.1)
The Traffic Signs Regulations and General Directions 2002 allows for speed limits to be imposed by local acts, but has never been used to impose speed limits on cyclists.
The speed limits in Royal Parks are also intended for motor vehicles only. According to The Royal Parks and Other Open Spaces (Amendment) etc. Regulations 2010 “vehicle” means a mechanically propelled vehicle intended or adapted for use on a road.
While, technically, cyclists do not have to adhere to speed limits, in practice it is most sensible and safe to do so. Cyclists who breach the speed limit may not be prosecuted for a speeding offence but, as stated above, can be prosecuted for “cycling furiously” or “wanton and furious driving.”