A caution that may be lodged at the Land Registry by any person claiming to have ownership of, or an interest in, unregistered land. The effect of the caution is to oblige the registrar to notify the cautioner of any application for first registration of that land, and of the cautioner's right to object to that registration. The cautioner then has 15 days to object. The owner of the legal estate to which the caution relates has a right to apply for cancellation of the caution, as do some others interested in the land. If the unregistered land could itself be registered in the name of the cautioner (for example, he has a freehold estate) then he should apply for first registration of the land himself, rather than lodging a caution.