You should bear in mind that breach of the rule does not prevent prosecution only conviction. In some circumstances, if the police have not complied with the law and have failed to serve the Notice and you can demonstrate this to them (with an authoritative letter setting out the relevant law and facts at an early stage of proceedings) it may be that they would consider dropping the case against you long before any trial. Of course, if they were to drop a case following receipt of such a letter this could save you a great deal of stress, costs and time as well as avoiding a conviction.