What is the standard of proof required to establish cruelty in a civil case?

This issue of the degree of proof has been and probably always will be the subject of judicial dialectics. In a matrimonial cause when concerned with the degree of proof required to establish cruelty, Denning, L.J., well said in Bater v. Bater, [1950] 2 All E.R. 458 at p. 459: The difference of opinion which has been evoked about the standard of proof in these cases may well turn out to be more a matter of words than anything else. It is true that by our law there is a higher standard of proof in criminal cases than in civil cases, but this is subject to the qualification that there is no absolute standard in either case. In criminal cases the charge must be proved beyond reasonable doubt, but there may be degrees of proof within that standard. Many great judges have said that, in proportion as the crime is enormous, so ought the proof to be clear. So also in civil cases. The case may be proved by a preponderance of probability, but there may be degrees of probability within that standard. The degree depends on the subject-matter. A civil court, when considering a charge of fraud, will naturally require a higher degree of probability than that which it would require if considering whether negligence were established. It does not adopt so high a degree as a criminal court, even when it is considering a charge of a criminal nature, but still it does require a degree of probability which is commensurate with the occasion.