(5) The duty payable on the death of the deceased by virtue of section 17 shall be a first charge by way of floating security on the assets which the company had at the death or has at any time thereafter, and any part of the duty for which by virtue of clause (c) of sub- section (1) any person is accountable in respect of any distributed assets shall be a first charge also on those assets: Provided that nothing in this sub- section shall operate to make any property chargeable as against a bona fide purchaser thereof for valuable consideration without notice.