4. If and whenever any of the payments mentioned in clause 2(1) of this licence or any part thereof are in arrears or unpaid for 28 days after any of the days whereon the same ought to be paid (whether the same has been legally demanded or not), then and so often as the same may happen the OGA may (as an additional remedy and without prejudice to any other rights and remedies to which they would be entitled) do diligence in respect thereof in like manner as a landlord may do diligence in respect of unpaid arrear of rent and such diligence may be effectual to attach all or any of the stocks of Petroleum, engines, machinery, tools, implements and other effects belonging to the Licensee which are found on or about any of the Licensee’s installations and equipment used or to be used in connection with searching, boring for or getting petroleum in the Licensed Area, and where in pursuance of such a diligence a sale of such effects as have been attached thereby takes place, the OGA may out of the proceeds thereof retain and pay all the arrears of the said payments and also the expenses of and incident to such diligence and sale and must then pay the surplus thereof (if any) to the Licensee.