The Protection of Animals Act
If any person—
(
(b)shall knowingly put or place, or cause or procure any person to put or place, or knowingly be a party to the putting or placing, in or upon any land or building any poison, or any fluid or edible matter (not being sown seed or grain) which has been rendered poisonous,
such person shall, upon summary conviction, be liable to a fine not exceeding [F14level 4 on the standard scale]
[F15 Provided that, in any proceedings under paragraph ( b ) of this section, it shall be a defence that the poison was placed by the accused for the purpose of destroying insects and other invertebrates, rats, mice, or other small ground vermin, where such is found to be necessary in the interests of public health, agriculture, or the preservation of other animals, domestic or wild, or for the purpose of manuring the land, and that he took all reasonable precautions to prevent injury thereby to dogs, cats, fowls, or other domestic animals and wild birds. ]