Blackmail S21(1) Theft Act 1968
A person commits the offence of blackmail if he or she makes any unwarranted demand with menaces, with a view of making a gain for him or herself or any other person, or with intent to cause loss to any other person.
The demands must be unwarranted and unreasonable, some demands may be considered reasonable e.g. repaying a debt
Points to prove for blackmail