Public Order Act 1986
5 Harassment, alarm or distress.
(1)A person is guilty of an offence if he—
(a)uses threatening, abusive or insulting words or behaviour, or disorderly behaviour, or
(b)displays any writing, sign or other visible representation which is threatening, abusive or insulting, within the hearing or sight of a person likely to be caused harassment, alarm or distress thereby.
(2)An offence under this section may be committed in a public or a private place, except that no offence is committed where the words or behaviour are used, or the writing, sign or other visible representation is displayed, by a person inside a dwelling and the other person is also inside that or another dwelling.
(3)It is a defence for the accused to prove—
(a)that he had no reason to believe that there was any person within hearing or sight who was likely to be caused harassment, alarm or distress, or
(b)that he was inside a dwelling and had no reason to believe that the words or behaviour used, or the writing, sign or other visible representation displayed, would be heard or seen by a person outside that or any other dwelling, or
(c)that his conduct was reasonable.
(4)A constable may arrest a person without warrant if—
(a)he engages in offensive conduct which constable warns him to stop, and
(b)he engages in further offensive conduct immediately or shortly after the warning.
(5)In subsection (4) “offensive conduct” means conduct the constable reasonably suspects to constitute an offence under this section, and the conduct mentioned in paragraph (a) and the further conduct need not be of the same nature.
(6)A person guilty of an offence under this section is liable on summary conviction to a fine not exceeding level 3 on the standard scale.