(1)It shall not be an objection to the validity of a real burden (whenever created) that—
(a)an amount payable in respect of an obligation to defray some cost is not specified in the constitutive deed; or
(b)a proportion or share payable in respect of an obligation to contribute towards some cost is not so specified provided that the way in which that proportion or share can be arrived at is so specified.
(2)Without prejudice to the generality of subsection (1) above, such specification may be by making reference to another document the terms of which are not reproduced in the deed; but for reference to be so made the other document must be a public document (that is to say, an enactment or a public register or some record or roll to which the public readily has access).