If this wall had been erected by the freeholder and taken down by the freeholder the next day, or a week, or a year afterwards, with the result that the flood water took the course which it would have taken if the wall had never been there, I cannot see, on any principle known to me, that the respondents would have been entitled to complain. If it were not so, a person, in putting up a defensive work on his own land, would act at his peril, because by the mere fact of erecting it he would be conferring on his neighbours, or persons in the neighbourhood, rights to insist that he should never remove the wall or building that he had put up.
He went on to say that "the respondents had no right to have the wall erected, they had no right to insist on its continuance, they had no ground of complaint whatsoever against anybody who rightfully took it down" [13] . The decision in that case was explained in Leakey v. National Trust [14] on the ground that there was nothing unreasonable in the action of the appellants in taking down the old protective wall on their own land in order to rebuild it. However, it seems to us, with all respect, that the judgment of Sir Wilfred Greene M.R. proceeded on the basis that the appellants had no duty to act reasonably. If there was such a duty, it must, in our opinion, have been created by the fact that the removal of the wall caused the flood water to flow onto the respondent's land. Where a person, by doing something on his own land, causes actual and material damage to another's land, the act of the first mentioned person, although otherwise lawful, may be actionable if it was unreasonable having regard to all the circumstances, including the effect it was likely to have on the other land. For example, the neighbour of a railway company may have no right to require the company to maintain an embankment, and the company may lawfully cut trenches in the embankment, but if it does so when the consequence is to cast flood waters onto the neighbour's land, the company may be liable: see Whalley v. Lancashire and Yorkshire Railway Co. [15] . A landowner may lawfully build a paved driveway on his land, but he may be liable in nuisance if he does so in such a way as to divert storm waters onto his neighbour's land: Bennetts v. Honroth [16] .
1. [1941] 1 K.B. 381.
2. [1941] 1 K.B., at p. 389.
3. [1941] 1 K.B., at p. 393.
4. [1980] Q.B. 485, at p. 522.
5. (1884) 13 Q.B.D. 131.
6. [1959] S.A.S.R. 170.