6. The railway shall be constructed and operated on a nominal gauge of 1.435 metres (4 feet 8½ inches) and the motive power shall be diesel, steam, internal combustion, battery electric or such other motive power as the Secretary of State may approve:
Provided that nothing in this Order shall authorise the use of electrical power as motive power on the railway unless such power is obtained from storage batteries or from a source of generation entirely contained in and carried along with the engines and carriages:
Provided also that, if electrical power is used as motive power on the railway, such electrical power shall not be used in such a manner as to cause or be likely to cause any interference with any telecommunications apparatus (as defined in Schedule 2 to the Telecommunications Act 1984(1) or with telecommunication by means of such apparatus.