“The words used as labels are seldom arbitrary. They are usually chosen as a distillation of the meaning or purpose of a concept intended to be more precisely stated in the definition. In such cases the language of the defined expression may help to elucidate ambiguities in the definition or other parts of the agreement.”
“The expression “derogation from grant” conjures up images of parchment and sealing wax, of copperplate handwriting and fusty title deeds. But the principle is not based on some ancient technicality of real property. As Younger LJ observed in Harmer v Jumbil (Nigeria) Tin Areas Ltd[1921] 1 Ch 200 at pp 225, 226, it is a principle which merely embodies in a legal maxim a rule of common honesty. It was imposed in the interest of fair dealing: A grantor having given a thing with one hand, as Bowen LJ put it in Birmingham, Dudley & District Banking Co v Ross, is not to take away the means of enjoying it with the other. If A lets a plot of land toB, as Lord Loreburn phrases it in Lyttelton Times Co v Warners, he may not act so as to frustrate thepurpose for which in the contemplation of both parties the land was hired. The rule is clear but thedifficulty is, as always, in its application. As one would expect, the principle applies to all forms of grants. It was applied recently by the House of Lords to the sale of a car by the manufacturer: see British Leyland Motor Corporation Ltd v Armstrong Patents Co Ltd[1986] AC 577 . The principle operates to restrict the future activities of a grantor. One field, and perhaps it was the earliest field, in which the principle finds expression is the grant by implication of easements over land retained by the grantor corresponding to the continuous or apparent quasi-easements enjoyed at the time of the grant over the property retained (see Parker J in Browne v Flower, at p 225). In such cases there must necessarily be retained land over which the easement being implied is to operate. Booth v Alcock (1873) 8 Ch App 663 is an example of this.”