Where a local authority claim to recover any sum in respect of rates or otherwise under or in pursuance of any provision of this Act from a person as being the owner of premises and that person proves that he—
(a)is receiving the rent merely as trustee, tutor, curator, factor or agent for some other person; and
(b)has not, and since the date of the service on him of the demand for payment has not had, in his hands on behalf of that other person sufficient money to discharge the whole demand of the authority,
his liability should be limited to the total amount of the money which he has or has had in his hands as aforesaid.