in any legal proceedings before the Appellate Board in which the relief sought includes alteration or rectification of the register or in which any question relating to the practice of the patent office is raised;

which is not opposed, and the application is either refused by the Controller or is accepted by him subject to any amendments, modifications, conditions or limitations, or

which has been opposed and the Controller considers that his appearance is necessary in the public interest,

and the Controller shall appear in any case if so directed by the Appellate Board.

(2)

Unless the Appellate Board otherwise directs, the Controller may, in lieu of appearing, submit a statement in writing signed by him, giving such particulars as he thinks proper of the proceedings before him relating to the matter in issue or of the grounds of any decision given by him or of the practice of the patent office in like cases, or of other matters relevant to the issues and within his knowledge as the Controller may deem it necessary, and such statement shall be evidence in the proceeding.