The undertaker may compulsorily acquire so much of the subsoil of the land referred to in paragraph (1) of article 18 as may be required for any purpose for which that land may be acquired under that provision instead of acquiring the whole of the land.

Where the undertaker acquires any part of the subsoil of land under paragraph (1) the undertaker shall not be required to acquire an interest in any other part of the land.

Paragraph (2) shall not prevent article 25 from applying where the undertaker acquires a cellar, vault, arch or other construction forming part of a house, building or factory.