For allegations of speeding detected by a remote device (e.g. a camera or a hand held speed gun) where the driver was not warned of a possible prosecution at the time the prosecuting authority must post, to the registered keeper (RK), a Notice of Intended Prosecution (NIP) so that, in normal circumstances, it will arrive within 14 days of the alleged offence (the day following the offence counting as day one).
The NIP is will be accompanied by a request for the RK to provide details of the driver at the time of the alleged offence (which he has to provide within 28 days or he will be guilty of an offence under Section 172 of the Road Traffic Act). It will also usually be accompanied by a conditional offer of a Fixed Penalty.