Protection from Harassment Act 1997
As of 1997, the Protection from Harassment Act came into force in the UK. Initially introduced to bolster the legislation preventing activities such as stalking, this Act is in effect an umbrella covering all forms of harassment.
“the test of harassment was held to be ‘conduct targeted at an individual which is calculated to produce the consequences described in section 7 and which is oppressive and unreasonable’ … Whether conduct is reasonable will depend upon the circumstances of the particular case.”
Iqbal v. Dean Mason Solicitors 
The law’s definition of harassment is wide-ranging and is not exhaustive, providing the opportunity for judgment on a case-by-case basis. In general, a person must not pursue a course of conduct which amounts to harassment of another, or which they ought to know amounts to harassment of that other.
A course of action will be considered harassment by the court if a reasonable person in possession of the same information would think the course of conduct amounted to harassment of the other.
There is, therefore, considerable scope for a wide range of claims against individuals and organisations. For example, if an individual has suffered harassment in the workplace they may choose to pursue action for damages under the Protection from Harassment Act rather than at an Employment Tribunal.
“the Act is concerned with courses of conduct which amount to harassment, rather than individual instances of harassment … it is the course of conduct which has to have the quality of amounting to harassment, rather than individual instances of conduct.”
Iqbal v. Dean Mason Solicitors 
If found guilty of an offence under the Protection from Harassment Act 1997, the defendant is liable to face imprisonment up to 6 months, a fine not exceeding level 5 on the standard scale (up to £5,000), or both. The legislation also allows the issuing of restraining orders.
If the defendant has a restraining order placed against them and they subsequently do anything they are prohibited from doing under the injunction, they may be sent to prison for up to 5 years.
“the purpose of the Act, it seems to me plain, is intended to render actionable conduct which might not be alarming if committed once, but becomes alarming by virtue of being repeated … It is, therefore, … not necessary for there to be alarm caused in relation to each of the incidents relied upon as forming part of the course of conduct. It is sufficient if, by virtue of the course of conduct, the victim is alarmed or distressed.”
Kelly v. Director of Public Prosecutions 
Damages may be awarded to the victim for (among other things) any anxiety caused by the harassment and any financial loss resulting from the harassment.
Threats of violence are also covered by the harassment Act, with severe consequences. A person who through their course of conduct causes another to fear, on at least two occasions, that violence will be used against him is guilty of an offence. If found guilty of an offence under this section, the defendant is liable to face imprisonment for a term not exceeding five years, or a fine, or both. If the guilty party is provided with a summary conviction, they may be imprisonment for a term not exceeding six months, fined, or both.
Malicious Communications Act 1998
Further to the Protection from Harassment Act, there is also legislation to prevent harassment involving malicious communications either through the post, by telephone, Fax, cyber-stalking or by SMS messages sent to mobiles.
Under this legislation it is an offence to send an indecent, offensive or threatening letter, electronic communication or other article to another person and under section 43 Telecommunications Act 1984 it is a similar offence to send a telephone message which is indecent offensive or threatening. Both offences are punishable with up to six months imprisonment, a fine, or both.