Per Lopes LJ in Royal Aquarium v Parkinson  1 QB 431 at p. 451:
The authorities establish beyond all question that neither party, witness, counsel, jury, nor judge can be put to answer civilly or criminally for words spoken in office; that no action of libel or slander lies, whether against judges, counsel, witnesses, or parties, for words written or spoken in the course of any proceedings before any Court recognised by law, and this though the words written or spoken were written or spoken maliciously, without any justification or excuse, and from personal ill-will and anger against the person defamed. This ‘absolute privilege’ has been conceded on the grounds of public policy, to insure freedom of speech where it is essential that freedom of speech should exist, and with the knowledge that Courts of justice are presided over by those who, from their high character, are not likely to abuse the privilege, and who have the power, and ought to have the will, to check any abuse of it by those who appear before them. It is, however, a privilege which ought not to be extended. It belongs, in my opinion, to Courts recognised by law, and to such Courts only.