Section 31
31. Registration to be prima facie evidence of validity.—
(1) In all legal proceedings relating to a trademark registered under this Act (including applications under section 57), the original registration of the trademark and of all subsequent assignments and transmissions of the trademark shall be prima facie evidence of the validity thereof.
(2) In all legal proceedings as aforesaid a registered trademark shall not be held to be invalid on the ground that it was not a registrable trademark under section 9 except upon evidence of distinctiveness and that such evidence was not submitted to the Registrar before registration if it is proved that the trademark had been so used by the registered proprietor or his predecessor in title as to have become distinctive at the date of registration.