A power of attorney given for valuable consideration may be given, and shall be deemed to have been always capable of being given, to a purchaser of property or any interest therein, and to the persons deriving title under him thereto, and those persons shall be the duly constituted attorneys for all the purposes of the power, but without prejudice to any right to appoint substitutes given by the power.
This section applies to powers of attorney created by instruments executed after the thirty-first day of December, eighteen hundred and eighty-two.
This section does not authorise the persons deriving title under the donee of the power to execute, on behalf of the registered proprietor, an instrument relating to registered land to which effect is to be given on the register, unless the power is protected by a caution or other entry on the register.