Regulation 18 requires an operator of an upper tier establishment to regularly send information to people liable to be affected by a major accident occurring there, without them having to request it. Regulation 19 requires the competent authority, the HSE or Office for Nuclear Regulation and one of the environment agencies (for England, Wales or Scotland), to adopt a procedure to deal with requests for information. Competent authorities have a range of powers, including imposing duties on groups of establishments, identified as “domino” groups, to co-operate. Domino groups arise where the risk or consequences of a major accident may be increased because of the geographical position of establishments; their proximity to each other; or the inventories of dangerous substances they hold.