J. Development required for the purposes of the Post Office consisting of—
(a)the installation of posting boxes or self-service machines,
(b)any other development carried out in, on, over or under the operational land of the undertaking.
J.1 Development is not permitted by Class J if—
(a)it would consist of or include the erection of a building, or the reconstruction or alteration of a building where its design or external appearance would be materially affected, or
(b)it would consist of or include the installation or erection by way of addition or replacement of any plant or machinery which would exceed 15 metres in height or the height of any existing plant or machinery, whichever is the greater.