Sch 1A para 12
(1) If shares or rights held by a person and shares or rights held by another person are the subject of a joint arrangement between those persons, each of them is treated for the purposes of this Schedule as holding the combined shares or rights of both of them. (2) A “joint arrangement” is an arrangement between the holders of shares (or rights) that they will exercise all or substantially all the rights conferred by their respective shares (or rights) jointly in a way that is pre-determined by the arrangement. (3) “ Arrangement ” has the meaning given by paragraph 21.