Subject to what has been said already, the broad general questions to be determined in each case are- (1) Whether the ancient lights of the plaintiff (or person complaining) have been illegally obstructed. (2) If so, what damage has been sustained in respect of the injury. For arriving at a just decision all relevant circumstances may be and should be taken into account.

All available sources of light should be considered, and it is nearly if not quite as important to know what is left as what is stopped by the building complained of.

Also the locality and the necessities as regards light for the windows of the dominant tenement, in order that it may be profitably or conveniently used for the purposes for which it is evidently designed may be considered. Special privileges for extra light in excess of what would ordinarily be presumed to be reasonable could only be allowed in cases where special circumstances could be proved, such as particular covenants actual or implied, or some special agreement to cover the excess claim.

In a general way it is not to be presumed that owners or occupiers of servient tenements are affected with knowledge of how the light is used after it has entered the windows of dominant tenements, or that they are concerned about any changes which may be made inside the building. It is a general rule that extra burdens should not be imposed upon servient tenements or their owners or occupiers without their consent, but facts from which consent may be presumed may often be proved.

The space available would not admit of any attempt to analyse or even to pass in rapid review the chief facts proved in the many reported cases which have been decided from time to time in the Law Courts, nor would any commensurate advantage be derived from any such attempt, because the facts and evidence of no two cases are exactly alike, and in some of the reported cases the judicial views of the principles applicable have not always been uniformly consistent.

A very large proportion of "Ancient Light" disputes are essentially matters for compromise, due regard being had for the comfort and convenience and legal rights of all persons concerned.

The legal rights are not in their nature sharply definable by any exact bounds. Lord Chancellor Halsbury, in his judgment in Colls v. Home & Colonial Stores, after saying that "The test of the right is, I think, whether the obstruction is a nuisance" goes on to say, "and it appears to me, the value of the test makes the amount of right acquired depend upon the surroundings and circumstances of light coming from other sources, as well as the question of the proximity of the premises complained of. What may be called the uncertainty of the test may also be described as its elasticity." Nearly all questions which may legitimately arise are of such a character that, with a right disposition on the part of the principal persons concerned, they can be best settled by inspection, inquiry, and consultation with experienced surveyors and architects. When light actions are tried in a Court of Law the issues are for the most part issues of fact, which would be determined by a Jury if there were one, or by the Judge acting as a Jury.

In a Court of Law the issues of fact are determined mainly by aid of plans, and the opinions and estimates of experts and others called to give evidence in Court, by the opposing parties. In many cases it would be more satisfactory if the main issues of fact could be ascertained and determined on the spot by competent professional assessors, or even by experts appointed by the parties and vested with responsibility to act as. judges of fact and as arbitrators, rather than as. partisans in a Court of Law.

It is, however, necessary that in all cases due regard should be had for the legal rights of the parties, otherwise there might be much haphazard injustice and confusion.

In concluding this chapter it may be as well to restate in epitomised form the chief principles of law affecting the nature and extent of the "Easement or Light."

(1) Every owner of land has a prima facie right tobuild on it, and to open any windows he pleases in any part of his buildings, and he has a free right to receive and take in and to use all the light he can get from any or every direction.

(2) Prima facie all neighbours have the same rights in these respects, so that if they choose to exercise their rights to build without consulting each other's interests or convenience or comfort they may hem each other in so as to make many or most of the windows useless; or if they like they may run up blank walls or erect hoarding or plant trees or hedges close to the borders of their land for the express purpose of obstructing the light to a neighbour's windows

(3) Sometimes a privilege is acquired for some windows in a covered building which entitles the owner or occupier of the premises to restrain neighbours from so building as to interfere with the privilege.

The privilege is called in law an Easement.

The tenement with the privileged windows is called the "dominant" tenement, and its owner the "dominant" owner. The privilege overrides and restrains the exercise of some of the natural rights of one or more neighbours. The tenements whose owners or occupiers are restrained from the exercise of their full natural rights because of the privilege attached to the windows are called "servient" tenements, and the owners "servient" owners.

(4) The privilege of the dominant implies a burden on the servient tenement One is benefited, the other is injured, by the existence of the easement.

When, therefore, a dispute arises between neighbours about an easement of light for particular windows, it may be necessary first to ascertain whether a claim for any privilege is well grounded ; and if it is found to be so, then the extent of the privilege should be inquired into, with due regard to the principle that no excessive burden should be imposed on the servient tenement or its owner or occupier without the consent of the servient owner clearly established.

(5) The general rule is that a prescription privilege (or Easement of Light) covers only so much light as is reasonable under the circumstances of the case, and the test to be applied when the action of a servient owner or occupier in building or otherwise diminishing the supply of light to the privileged window comes up for consideration and decision is whether his action is of such a character as to constitute a nuisance.

Very small or unsubstantial interference with light to a privileged window will not suffice for a ground of action, on the general principle de minimis non curat lex, and even substantial interference with the lighting of privileged windows may not necessarily suffice to give a ground of action ; there must be in addition real substantial injury to the person complaining, or to the value of his property.

(6) The privilege does not confer any claim for a good outlook or prospect from the windows, nor any right to demand an uninterrupted view towards the windows from the side or in any other particular direction. It is concerned only with the access of a reasonable sufficiency of light to the windows.