Business interruption insurance proviso requiring that, before a claim can be allowed, a material damage claim must be admitted; the absence of such insurance would prolong the interruption. When the interruption results from damage at external premises, e.g. the supplier’s, the only requirement is that the damage should have been caused by an insured peril. See CUSTOMERS’ EXTENSION; SUPPLIERS’ EXTENSION; LOSS OF ATTRACTION; DENIAL OF ACCESS; EXTERNAL DEPENDENCIES.