means an unconditional, irrevocable standby Letter of Credit substantially in the form set out in Annex M-1 (or such other form as the Panel may approve) in sterling in favour of the BSC Clearer by any United Kingdom clearing bank or banks or any other bank or banks which has (have) a long term debt rating of not less than single A by Standard & Poor’s Corporation or by Moody’s Investors Service, Inc. or such other bank or banks as the Panel may approve, and which shall be available for payment at a London branch of the issuing bank;