reg 4 Requirement for authorisation
(1) No person is to put into use any structural subsystem unless— (a) the Safety Authority has given an authorisation under these Regulations for the placing in service of that subsystem; or (b) the Competent Authority has decided under regulation 13 that for the upgrading or renewal of the subsystem, an authorisation is not required for the subsystem to be put into use; ... (c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (2) A structural subsystem is put into use when, having been constructed, upgraded or renewed, it is first used on or as part of the rail system ... for the transportation of passengers or freight or for the purpose for which it was designed. (3) For the purposes of paragraph (2) use of a structural subsystem does not include any testing or trials conducted in the relevant EC or UK verification assessment procedure or for additional checks required by the Safety Authority. (4) The requirements set out in paragraph (1) apply to a vehicle even if there is an extant authorisation granted in an EU Member State or by the European Union Agency for Railways. A person wishing to put a vehicle into use in the UK beyond the Channel Tunnel system which has such an authorisation must apply for an authorisation under regulation 6.