This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol3", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Such invasion of privacy is not recognised as an actionable wrong, so that if the people affected cannot erect screens on their own grounds to stop the overlooking, and thus preserve privacy, there may be no alternative but to submit to the annoyance.
Also, it must be understood that an easement of light does not confer a right of prospect, - or in other words, there is no easement of view or prospect, so that a neighbouring owner or occupier of land may plant trees or hedges or erect buildings in positions which will more or less entirely shut out distant view, if he does not at the same time diminish to an actionable extent the quantity of light which can reach the window. In this connection it may be noted that the amount of light which may reach a window by reflection from a distant landscape is generally a very exceedingly small proportion of the light reaching the window from the sky, and if the physical geography of the neighbourhood permits, the prospect may often be blocked or otherwise spoilt without any actionable invasion of the easement. No question of any right to uninterrupted prospect can arise except under some kind of special contract binding upon the obstructor.
From what has been already said it can be understood how easily neighbouring landlords and householders may cause great inconvenience and annoyance to each other, and real injury to the value of each other's tenements, while keeping within their strictly legal rights. It will also be evident how the possession of an easement of light by one tenement may confer an immense advantage and create a corresponding disadvantageous condition for neighbouring tenements not similarly favoured. It is therefore most important for nearly all persons proposing to deal with house property to take careful note of all easements of light, and to remember that an easement, by its very nature, appertains to the tenement to which it belongs, and is inseparable from it, so that when the tenement is transferred from one owner to another the easement is transferred with the tenement, and the owner for the time being can claim and enforce the privilege. The easement is said to run with the land.
Owners of neighbouring properties may make personal contracts with each other, and they may be personally bound by their contracts, and also some other persons deriving title from them may in certain events be bound by those contracts, when affected with notice under circumstances from which it may fairly be held that they had adopted the contracts ; but in a general way mere personal agreements between neighbours to abstain from interfering with each other's privacy or prospect, or in other ways to consult each other's convenience when building or altering their tenements, will not of themselves suffice to secure the properties from the accrual of rights of easement which may more or less seriously hamper the same or other owners in future, and cause ultimate depreciation of the value of the property.
For a full understanding of the nature of the right, it is necessary to take note of the peculiar characteristics which distinguish light from other casements. In the first place, it is what is called a Negative Easement, which does not confer on the owner or occupier of the dominant tenement any sort of right to enter upon any portion of the servient tenement to do anything there. The dominant owner is simply entitled to receive the light upon his own land through the particular openings or windows for which he has acquired an easement or special privilege, as before explained. As with other easements, he cannot require the servient owner to do anything to help him to obtain the light he wants, or indeed to do anything at all. He can only require that his neighbours shall not illegally interrupt the access of light to his privileged window spaces.
Also, the owner whose building receives light is under no obligation to provide for its passing out again. The light is received for use, and may, if desired, be all used up. It is drawn from the common universal stock from which all men are entitled to help themselves whenever they can do so without trespassing upon their neighbour's rights. Evidently, from the very nature and distribution of light through space, any quantity which could be taken in through any window or any definite number of windows would be altogether inappreciable by comparison with the total quantity of light available for the rest of mankind. There can therefore never be a question of injury to anybody from the quantity of light taken in and consumed, any more than any one could complain of injury from the consumption of oceanic water in the boilers of ocean-going steamers. But although no one can legally complain of the quantity of light received or used, any neighbour is entitled to dispute a claim to restrain his actions in building upon his own land. It is open to a neighbour whose conduct is complained of to deny that any easement has been acquired or remains in existence at the time, or to say that under the circumstances he has not given to plaintiff any just cause of complaint. As before stated, if no easement over his land for any particular openings or windows could be proved, the neighbour would be under no obligation to let any light pass over his land to the windows ; but if an easement over his land were proved, he must then certainly let some light pass, and regulate his building operations accordingly, but it would still be an open question how much light he must let pass across his land. Disputes concerning the extent of the right have been very numerous, and there would seem to have been considerable variations from time to time, and consequent apparent uncertainty about the principles applicable for the decision of such cases. Considerable differences in the facts alleged and proved in different cases, and more particularly some peculiarities in the wording of those sections of the Prescription Act which relate to Light, have been in the main responsible for such apparent conflict of authority.