In the event of loss or damage to the Property Insured under this policy for which liability is admitted and payment made the insurance hereunder shall notwithstanding be maintained in force for the remainder of the Period of Insurance at the Total Sum Insured as stated in the Schedule for section I subject to the Insured undertaking to pay an additional premium calculated at the Policy Rate on the amount of the loss pro rata from the date of such loss to expire date of the Period of Insurance.