(b) that the tenant has, on or after the 9th day of June, 1952 , sub- let, assigned or otherwise parted with the possession of the whole or any part of the premises without obtaining the consent in writing of the landlord. Explanation.- For the purpose of this clause, any premises which have been let for being used for the purposes of business or profession shall be deemed to have been sub- let by the tenant, if the Rent Authority is satisfied that the tenant, without obtaining the consent in writing of the landlord, has, after the 16th day of August, 1958 , allowed any person to occupy the whole or any part of the premises ostensibly on the ground, that such person is a partner of the tenant in the business or profession but really for the purpose of sub- letting such premises to that person;