Monsanto v Tilly [1999] EWCA Civ 3044
Availability of defence of necessity for trespass to land
Facts
The claimant was a company that had been granted a licence by the government to carry research into genetically modified crops for the food industry. The defendant was a member of a group set up to campaign against genetically modified food stuffs. The group had a genuinely held belief that the use of these crops posed a risk to public safety. However, in order to advance its campaign the defendant’s group uprooted the crops planted with the hope of gaining publicity. The claimant sought an injunction preventing the defendant’s trespass. The defendant contended that the group’s actions were necessary for the protection of third parties and the public and at first instance the defendant was given unconditional leave to defend an action in trespass on this basis. The claimant appealed.
Issues
The issue in this context was whether the defence of necessity was available to the defendant in trespass as against the claimants application for an injunction.
Decision/Outcome
It was held that the defence of necessity was not available to the defendant. In exceptional circumstances, a person could enter land without licence to prevent serious and immediate danger. In the circumstances here, this point may have been arguable if the entire crop had been uprooted. However, the defendant had only uprooted part of the crop and it was considered that this was done for publicity purposes, rather than for the protection of the public. Furthermore, even if the situation was considered an emergency, trespass was not justifiable where a public authority was responsible for the public interest.
Updated 21 March 2026
This case summary remains accurate as a statement of the 1999 Court of Appeal decision in Monsanto v Tilly [1999] EWCA Civ 3044. The legal principles described — that necessity is available as a defence to trespass to land only in very limited circumstances, and that it will not succeed where the defendant’s purpose was publicity rather than genuine emergency prevention, or where a public authority bears responsibility for the public interest — continue to reflect the law as understood in English tort law. No subsequent legislation or appellate authority appears to have materially altered or overruled the position established in this case. Students should note that the defence of necessity in tort remains narrow and fact-sensitive, and that this case is frequently cited in that context.
