“The presumption is, at least normally, a presumption of fact, not law, and as such it is rebuttable by evidence to the contrary. Thus viewed, the term “presumption of fact” is in my judgment something of a misnomer, because such a presumption does not shift the persuasive evidential burden of proof on the relevant issue, but merely “describes the readiness of the court to draw certain repeated inferences as a result of common human experience”: see Phipson on Evidence, 17th edition… Not only are presumptions of fact always rebuttable, but the trier of fact may refuse to make the usual natural inference, notwithstanding that there is no rebutting evidence.”
“… The presumption is no more than a rebuttable statement founded on common sense, of the inference it will normally be appropriate to draw in a given situation where primary evidence is lacking.”