The legislative purpose of the requirement to serve a NIP is to enable the accused to identify and recall the incident in question while it is still relatively fresh in his mind, and to potentially enable him to gather and preserve any evidence that might assist any defence.
Whilst the requirement to serve a NIP within the 14 days (where applicable) is mandatory, the required details are merely directory.
The above is mostly my synopsis of Pope v Clarke - before the RTA exception was added to the statute, driver hit a lorry, spoken to by the police but not warned he might be prosecuted, subsequently received a NIP describing the nature and location of the incident but with the time several hours out.
Whether the nature of the offence was adequately identified would be a matter of fact and degree, and should be determined with regard to the above. N.B. the nature of the alleged offence does not need to include the specific offence being prosecuted (and in some cases, it would appear to be arguable that a specific offence such as careless driving would be too vague to convey the nature of the allegation).
If the nature of the offence is using a hand-held mobile phone while driving, and that is conveyed by the NIP, job done.
