None of the cases relating to mesne profits to which I have referred deals with a situation precisely the same as that which presents itself in this case. It is true, of course, that the cases consistently predicate that the plaintiff must establish that he has entered into possession of the subject premises. And they do so in language which suggests that the accrual to the plaintiff of a cause of action for mesne profits is dependant upon the occurrence of such an event. But none of the cases, as far as I can see, contemplated a situation such as the present where the writ was issued before entry and an entry, in turn, preceded the trial. This case is, perhaps, made even more unusual by the fact that the plaintiff had obtained a warrant of possession some years before the date when the suit was instituted. The immediate question, however, is whether a claim for mesne profits made independently of proceedings for possession must fail if it is made before the plaintiff obtains possession of the subject premises. The answer to this question must, I think, be in the affirmative unless the fiction upon which trespass by relation is erected can be made to do double duty. Upon entry the plaintiff's possession is said to relate back by virtue of the legal fiction to the time when his right to possession arose. Can the plaintiff, then, in these proceedings, having entered after the issue of the writ, assert by force of the fiction that he was in possession at the date of the writ and, therefore, that his cause of action had then accrued? Or, perhaps, to put it in another way, is a plaintiff, upon entering into possession, entitled to assert that, thereupon, he became entitled to mesne profits "at the time when they arose"? (Ocean Accident and Guarantee Corporation v. Ilford Gas Company [1] ). It is, however, the contention of the companies that they are entitled to judgment if it appears that if the matter had been investigated at the date of the commencement of the suit it would have been found that the plaintiff's cause of action had not then accrued. To my mind principle and authority admit of only one answer to the problem; it is incumbent upon the plaintiff to establish the existence of his cause of action as at the date of his writ and the failure or success of his action will not depend upon whether the trial takes place promptly or happens to be delayed until after he has entered into possession. It seems to me that the problem is analogous to that which has arisen in cases where a plaintiff has, before actual grant of administration, commenced proceedings as an administrator. Notwithstanding that upon grant the administrator's title relates back to the death of the deceased whom he represents it has been consistently held that this element of retroactivity is incapable of sustaining a writ issued before grant (Chetty v. Chetty [2] ; Ingall v. Moran [3] ; Hilton v. Sutton Steam Laundry [4] ; and Finnegan v. Cementation Co. Ltd. [5] ).