Opinion as to existence of right or custom when relevant
50.  When the court has to form an opinion as to the existence of any general custom or right, the opinions as to the existence of such custom or right of persons who would be likely to know of its existence, if it existed, are relevant.
     Explanation.—“General custom or right” includes customs or rights common to any considerable class of persons.
Illustration
     The right of the inhabitants of a particular kampong to use the water of a particular well is a general right within the meaning of this section.