Herring, Criminal Law: Text, Cases, and Materials (8 edn, 2018). p. 75
What does ‘imminent’ mean?
The victim’s apprehension must be of imminent harm. It is well established that a threat to be violent in the distant future (e.g. ‘I will beat you up next week’) is not an assault.13 But what about a threat to cause violence in the near future? Lord Steyn in Ireland indicated that a fear of violence ‘within a minute or two’ might be sufficient to constitute an assault.14 This leaves open the question of exactly where the line is to be drawn: is fear of violence in ten minutes enough, an hour, a day? We can know only when we have further guidance from the courts.
13 But there are some specific offences that relate to threats to harm in the future, e.g. there is an offence of threatening to kill in the Offences Against the Person Act 1861, s. 16. 14 See also Smith v Superintendent of Woking Police Station (1983) 76 Cr App R 234.
Why isn't "a threat to be violent in the distant future (e.g. ‘I will beat you up next week’)" an assault? Please don't just answer "because courts have judged they're not, or UK Parliament hasn't criminalized this."