11. The Foundation shall have relief, under arrangements made by the Commissioners of Customs and Excise, by way of refund of duty (whether of customs or excise) paid on imported hydrocarbon oil (within the meaning of the Hydrocarbon Oil Duties Act 1979) or value added tax paid on the importation of such oil which is bought in the United Kingdom by the Foundation and necessary for the exercise of its official activities, such relief to be subject to compliance with such conditions as may be imposed in accordance with the arrangements.