Restriction on executory limitations

Where there is a person entitled to, (a) an equitable interest in land for an estate in fee simple or for any less interest not being an entailed interest; or (b) any interest in other property not being an with an executory limitation over on default or failure of all or any of his issue, whether within or at any specified period of time or not, that executory limitation shall be or become void and incapable of taking effect, if and as soon as there is living any issue who has attained the age of eighteen years of the class on default or failure whereof the limitation over was to take effect.