“If in action at law, decree or judgment should be given against the Insured in respect of any claim or claims arising out of any one accident or number of accidents as a foresaid for a sum or sums (exclusive of costs) in excess of the amount of the Single Accident Indemnity Limit the Insured shall pay such excess and the liability of the Company to pay costs shall be limited to an amount of the total costs as to as the Single Accident Indemnity Limit bears to the total sum or sums decreed or adjudged as aforesaid”