69 The statutory definition continues to be illuminated by the classic test of market value in relation to compensation for the resumption of land in Spencer v The Commonwealth (1907) 5 CLR 418. Isaacs J said at 441-442:
In the first place the ultimate question is, what was the value of the land on 1st January 1905?
All circumstances subsequently arising are to be ignored. Whether the land becomes more valuable or less valuable afterwards is immaterial. Its value is fixed by Statute as on that day. Prosperity unexpected, or depression which no man would ever have anticipated, if happening after the date named, must be alike disregarded. The facts existing on 1st January 1905 are the only relevant facts, and the all important fact on that day is the opinion regarding the fair price of the land, which a hypothetical prudent purchaser would entertain, if he desired to purchase it for the most advantageous purpose for which it was adapted. The plaintiff is to be compensated; therefore he is to receive the money equivalent to the loss he has sustained by deprivation of his land, and that loss, apart from special damage not here claimed, cannot exceed what such a prudent purchaser would be prepared to give him. To arrive at the value of the land at that date, we have, as I conceive, to suppose it sold then, not by means of a forced sale, but by voluntary bargaining between the plaintiff and a purchaser, willing to trade, but neither of them so anxious to do so that he would overlook any ordinary business consideration. We must further suppose both to be perfectly acquainted with the land, and cognizant of all circumstances which might affect its value, either advantageously or prejudicially, including its situation, character, quality, proximity to conveniences or inconveniences, its surrounding features, the then present demand for land, and the likelihood, as then appearing to persons best capable of forming an opinion, of a rise or fall for what reason soever in the amount which one would otherwise be willing to fix as the value of the property.
70 Griffiths CJ at 432 described the mental process as follows:
…to put yourself as far as possible in the position of persons conversant with the subject at the relevant time, and from that point of view to ascertain what, according to the then current opinion of land values, a purchaser would have had to offer for the land to induce…a willing vendor to sell it, or, in other words, to inquire at what point a desirous purchaser and a not unwilling vendor would come together.