306Property Law

land do not apply to a fee simple interest subject to a condition subsequent, and section 7 of the 1925 Act specifically provides that a fee simple subject to a right of entry is to be treated as a fee simple absolute (i.e. not subject to a contingency) and is therefore capable of being legal rather than merely equitable (a distinction we consider further in section 8.3 below).

The second difference is in the attitude of the law. A determinable contingency is regarded more or less neutrally, as an event marking the passing of benefit from one person to another. Rights of entry or forfeiture, on the other hand, are regarded as essentially punitive. The contingency making them exercisable tends to be a breach of an obligation, or the happening of an event which the grantor of the interest wanted to discourage (classically in family settlements, inappropriately marrying or not marrying). This has led to two consequences. The first is that the courts have tended to construe conditions subsequent much more strictly than determinable conditions. The second is that equity has evolved an extensive jurisdiction to grant relief against forfeiture of an interest by the exercise of a right of entry or forfeiture, on the basis that the right was conferred only as security for performance of the obligation, and if that can be secured in some other way, the interest ought to be allowed to continue.

8.2.5.3. Distinguishing determinable and forfeitable interests

Despite this real distinction between determinable and forfeitable interests, and the very real difference in their consequences and effects, the courts have traditionally regarded it as a matter of form rather than substance, allowing it to depend on the wording used rather than the intention of the grantor. So, a grant of a right to enjoyment ‘during’ a state of affairs, or ‘while’ it continues or even ‘until’ it stops, will usually be taken to create a determinable interest, automatically ending when the contingency arises, while a right of enjoyment ‘provided that’ or ‘on condition that’ a future event does not happen, or ‘but [terminable] if’ it does happen, will create an interest subject to a condition subsequent.

8.2.6. Requirement of certainty

Whether a contingency triggers off enjoyment, measures the duration of an interest, or confers on someone a right to terminate it prematurely, the contingency must be certain. If it is not certain, it will be void, the consequences of which are considered in section 8.2.7 below.

However, ‘certainty’ is a notoriously slippery concept. The basic rule in this context is that a contingency must be certain in the sense of being objectively ascertainable as a matter of fact, even if difficult to prove in practice. So, if I give you an option to buy my land next Wednesday ‘if the weather is bad on the immediately preceding Tuesday’, your option is void because the contingency is uncertain: bad weather is a matter of opinion not a matter of fact (‘if more than one inch of rain falls in my garden on Tuesday’ would do). Another way of putting it, and one that makes sense of the rule, is that the contingency must be