Prerogative of Mercy

In the English and British tradition, the royal prerogative of mercy is one of the historic royal prerogatives of the British monarch, in which he or she can grant pardons (informally known as a royal pardon) to convicted persons. The royal prerogative of mercy was originally used to permit the monarch to withdraw, or provide alternatives to death sentences; the alternative of penal transportation to "partes abroade" has been used since at least 1617. It is now used to change any sentence or penalty.

Officially, this is a power of the monarch. Formally, in Commonwealth realms, this has been delegated to the Governor-General of the realm, which in practice means to government ministers who advise the monarch or viceroy, usually those responsible for justice. Specifically, it has been delegated to the Lord Chancellor in England and Wales; the Scottish Ministers in Scotland; the federal cabinet in Canada; the Minister of Justice in New Zealand; and the Attorney-General or Minister for Justice in Australia.

In the important case of Derek Bentley, a court found that this royal prerogative power is "probably" entirely a matter of policy, and thus not justiciable.

The royal pardon can be contrasted with the statutory pardon, which is a pardon issued through an Act of Parliament or an Order-in-Council. The statutory pardon is preferred in most cases. In the United Kingdom, only four royal pardons have been granted since the end of World War II.

...
Wikipedia