What is the test for a defence of insanity in criminal law?

In support of his statement the learned author cites Woolmington v. Director of Public Prosecutions, [1935] A.C. 462, 25 Cr. App. R. 72, and quotes the classic statement of Viscount Sankey L.C. found on pp. 481-2, namely: “Throughout the web of the English Criminal Law one golden thread is always to be seen, that it is the duty of the prosecution to prove the prisoner’s guilt subject to what I have already said as to the defence of insanity and subject also to any statutory exception. If, at the end of and on the whole of the case, there is a reasonable doubt, created by the evidence given by either the prosecution or the prisoner, as to whether the prisoner killed the deceased with a malicious intention, the prosecution has not made out the case and the prisoner is entitled to an acquittal. No matter what the charge or where the trial, the principle that the prosecution must prove the guilt of the prisoner is part of the common law of England and no attempt to whittle it down can be entertained.” (The italics are mine.)