I'm rather surprised by several posters stating as fact that these activists revealing JKR's specific address on social media as an incitement to harass her and also being outside her private house with the purpose of causing her fear and distress isn't an offence because even a cursory Google would indicate that it comes under a number of offences -
www.cps.gov.uk/legal-guidance/social-media-guidelines-prosecuting-cases-involving-communications-sent-social-media
www.cps.gov.uk/legal-guidance/stalking-and-harassment
In particular -
'Harassment of a person in their own Home
Section 126 of the SOCPA amended the Criminal Justice and Police Act 2001(CJPA) and created a new offence of causing harassment, alarm or distress to a person in his or her home. The offence contains four ingredients which need to be proved. A person will commit an offence under section 42A(1) if:
• he or she is present outside or in the vicinity of any premises that are used as a dwelling;
• he or she is there to represent to the resident or another individual or persuade the resident or another individual that he should not do something he is entitled to do; or that he or she should do something he is not under any obligation to do;
• the person intends his presence to amount to the harassment of, or to cause alarm or distress to the resident; or knows or ought to know that his presence is likely to do so; and
• the presence of the defendant amounts to the harassment of, or causes alarm or distress to the resident, a person in the resident's dwelling, or a person in another dwelling in the vicinity of the resident's dwelling; or is likely to result in the harassment of, or cause alarm or distress of any such person.
The purpose of this offence is to give the police the ability to deal with harassing or intimidatory behaviour by individuals towards a person in his home even after an incident has taken place. This means that the police can deal with protestors after the event. This will be useful if, for example, there is evidence of a protest on CCTV but the police were not present, or the police were present and could identify the protestors but there was some difficulty in enforcing a direction at the scene of the protest.
The offence in section 42A of the CJPA might be used where, for example, protestors had conducted a rooftop protest at a person's home. If the police were not in attendance, but the resident had CCTV evidence of particular individuals on the roof of his house, and he had been harassed, alarmed or distressed by the presence of the protestors, the police could arrest the suspects for the new offence.
The penalty for this offence is imprisonment for a term not exceeding six months or a fine not exceeding level 4 on the standard scale or both.
Section 42A(2) of the CJPA defines persons who can be subjected to harassment, alarm or distress by the presence of others at their home. They are the resident; a person in the resident's dwelling, for example, a child or partner; and a person in another dwelling in the vicinity of the resident's dwelling, i.e. a neighbour.
There is no legal definition of "vicinity" and ultimately it is for the courts to determine what is meant by it as a matter of fact.'