Blackmail as defined in s21 Theft Act 1968 — common mistakes

In an exam, clearly separate the two limbs of the 'unwarranted' test. Even if a defendant genuinely believes they are owed money (satisfying the first limb), they will almost certainly be guilty if they use threats of violence, as they cannot genuinely believe this is a 'proper' means of recovery (failing the second limb).

Not necessarily. The primary test for 'menaces' is objective: would the threat affect a person of 'normal stability and courage'? If the victim is unusually brave and is not affected, it can still be blackmail if an ordinary person would have been. The only time the victim's specific character matters is if they are known to the defendant to be particularly timid, in which case the threat is judged by its effect on them.

Yes, it can. This is a common misconception. To avoid being 'unwarranted', you must believe you have reasonable grounds for the demand (which you do) AND that using menaces is a 'proper' means of reinforcing it. Threatening violence or exposure to ruin their reputation is not a 'proper' means. As established in R v Harvey (1981), a belief in the propriety of such threats is unlikely to be seen as genuinely held.

No. The offence of blackmail is complete the moment the unwarranted demand with menaces is made. The mens rea only requires a 'view to gain' or 'intent to cause loss', not that the gain or loss actually occurs. The success or failure of the demand is irrelevant to guilt, although it may affect sentencing.