Section 5: The provisions of section 3 shall not apply-

(a) to the user of a motor vehicle owned by Government or by the Imperial Government while such motor vehicle is being use~ for the purposes of the Government owning such rnotor vehicle; or (b) to the user of a passenger vehicle owned by a person who has deposited or keeps deposited with the Accountant General the sum of twenty-five thousand pounds or of any other vehicle owned by a person who has so deposited the sum of five thousand pounds in respect of such a motor vehicle at any time when such motor vehicle is being driven by the owner or by a servant of the owner in the course of his employment or is otherwise subject to the control of the owner; or (c) to the user of a motor vehicle at any time when it is driven for police purposes hy or under the direction of a superior police officer. Exemptions.