P climbed a high fence to trespass onto D’s land, climbed onto D’s roof and, because the roof was dangerous, fell through and was injured. D did not know that P was or might come onto the roof. P claimed that the words “reason able grounds to believe” from s.1(3)(b) means “ought to know” and therefore that it was no defence for D to state that he did not know that P was or might climb onto the roof. CA dismissed the claim, stating that actual knowledge was required and that “reasonable grounds to believe” did NOT equal “ought to know”.
Pill LJ: “Reasonable grounds to believe” means that, aside from actual knowledge, O also owes a duty if he knows of all the facts from which he can draw the inference that NV might enter the vicinity but chooses to “turn a blind eye. “A man cannot claim he has no knowledge when he has shut his eyes to the obvious. Nor can he claim that he has no knowledge when he has knowledge of what are sometimes called primary facts and has not drawn the inferences which can reasonably be drawn from those primary facts”. Here D did not have reasonable grounds to believe or actual knowledge that P could or might enter the vicinity of the danger and therefore no duty was owed. ‘Reasonable grounds to believe’ does NOT mean ‘ought to have been aware’.