BentMikey said:This bit is entirely wrong. You cannot be charged with speeding on most public highways because the law specifically applies to motor vehicles, and not to bicycles. You can be charged with speeding in places such as Richmond Park where the byelaws do cover bicycles as well. That's the case whether or not you have a speedometer.
If a cyclist is travelling at speeds in excess of a restriction it would be easy to demonstrate that the rider was guilty of either 'reckless cycling' or 'careless cycling' as determined by the Road Traffic Act 1988 which carry maximum fines of £2500 and £1000 respectively.