(1) Where an appeal is made in relation to -
(a) a decision of a Revenue officer on an apportionment,
(b) a determination of an amount referred to in section 100A, or
(c) a decision of an inspector under section 121(7),
and the decision or determination affects the liability to tax of a person, other than a person in respect of whom the decision or determination was made, each person so affected may apply to the Appeal Commissioners for, and the Appeal Commissioners on the making of such an application may give, a direction making the person a party to the appeal.
(2) Save insofar as that provision is inconsistent with subsection (1), each provision of section 949E shall apply to a direction under this section.