21.—(1) Where two or more persons with duties under Article 25 or 26 share, or have duties in respect of, relevant premises (whether on a temporary or a permanent basis) each such person shall—
(a)co-operate with the other persons concerned so far as is necessary to enable them to comply with the requirements and prohibitions imposed on them by or under these Regulations and the 2006 Order;
(b)(taking into account the nature of his activities) take all reasonable steps to co-ordinate the measures he takes to comply with the requirements and prohibitions imposed on him by or under these Regulations and the 2006 Order with the measures the other persons are taking to comply with the requirements and prohibitions imposed on them by or under these Regulations and the 2006 Order; and
(c)take all reasonable steps to inform the other persons with duties under Article 25 or 26 concerned of the risks to relevant persons arising out of or in connection with the conduct by him of his undertaking.
(2) Where two or more persons with duties under Article 25 or 26 share relevant premises (whether on a temporary or a permanent basis) where an explosive atmosphere may occur, the person with such duties who has overall responsibility for the relevant premises shall co-ordinate the implementation of all the measures required by fire safety duties to be taken to protect relevant persons from any risk from the explosive atmosphere.