In Cave v Robinson Jarvis & Rolf  UKHL 18,  1 AC 384, Lord Scott (at para 60) defined what proof the claimant is to submit to satisfy conditions of section 32(1)(b) of the Limitation Act 1980 with regard to deliberate concealment:
…deliberate concealment for section 32(1)(b) purposes may be brought about by an act or an omission and that, in either case, the result of the act or omission, i.e. the concealment, must be an intended result…A claimant who proposes to invoke section 32(1)(b) in order to defeat a Limitation Act defence must prove the facts necessary to bring the case within the paragraph. He can do so if he can show that some fact relevant to his right of action has been concealed from him either by a positive act of concealment or by a withholding of relevant information, but, in either case, with the intention of concealing the fact or facts in question. In many cases the requisite proof of intention might be quite difficult to provide. The standard of proof would be the usual balance of probabilities standard and inferences could of course be drawn from suitable primary facts but, nonetheless, proof of intention, particularly where an omission rather than a positive act is relied on, is often difficult.
Lord Millett in his turn said:
In my opinion, section 32 deprives a defendant of a limitation defence in two situations: (i) where he takes active steps to conceal his own breach of duty after he has become aware of it; and (ii) where he is guilty of deliberate wrongdoing and conceals or fails to disclose it in circumstances where it is unlikely to be discovered for some time. But it does not deprive a defendant of a limitation defence where he is charged with negligence if, being unaware of his error or that he has failed to take proper care, there has been nothing for him to disclose.