Well I would read it differently
The second bit is akin to going equipped to commit an offence. If the meter &/or cut=out seal has been tampered with and someone is in possession of a screw driver it could be used as evidence.
or(b)prevents any such meter from duly registering the quantity of electricity supplied,he shall be liable on summary conviction to a fine not exceeding level 3 on the standard scale.
(2)Where any person is prosecuted for an offence under sub-paragraph (1) above, the possession by him of artificial means for causing an alteration of the register of the meter or, as the case may be, the prevention of the meter from duly registering shall, if the meter was in his custody or under his control, be prima facie evidence (or in Scotland sufficient evidence) that the alteration or prevention was intentionally caused by him
The second bit is akin to going equipped to commit an offence. If the meter &/or cut=out seal has been tampered with and someone is in possession of a screw driver it could be used as evidence.