ABSTRACT
This involves situations where the testator or settlor expressed the class of objects so broadly that it becomes difficult for the court to ascertain any sensible exercise of the discretion. In the event of the trustees failing to exercise their discretion, the court may find it difficult to exercise it in a rational manner, for example, a duty to distribute a fund in favour of such of the residents of Greater London as the trustees may decide in their absolute discretion. This type of uncertainty does not affect the validity of powers of appointment (see Re Manisty) but has the effect of invalidating trusts.
