Where an assessment is made on a custodian under paragraph 1 of this Part of this Schedule in respect of any income, or any income which is paid subject to deduction of income tax is received by a custodian, and, in either case, it is shown to the satisfaction of the Commissioners of Inland Revenue that, but for the operation of the law relating to trading with the enemy, the person who, but for the operation of that law, would have been assessable to, or would have borne, the tax on that income, would, if a claim were made in that behalf, have been granted relief from all or any of the tax the same relief shall be granted to the custodian by repayment or otherwise.