Section 21 is mandatory in its terms and as it stood at the material time it provided as follows: "21(1) In the case of assets chargeable to tax under this Act which are held by a court of wards or an administrator general or an official trustee or any receiver or manager or any other person, by whatever name called, appointed under any order of a court to manage property on behalf of another, or any trustee appointed under a trust declared by a duly executed instrument in writing, whether testa mentary or otherwise (including a trustee under a valid deed of wakf), the wealth tax shall be levied upon and recoverable from the court of wards, administrator general, official trustee, receiver, manager or trus tee, as the case may be, in the like manner and to the same extent as it would be leviable upon and recoverable from the person on whose behalf the assets are held, and the provisions of the Act shall apply accordingly.