‘A’ intentionally and falsely led ‘B’ to believe that a plot of land belonged to him. On that basis, he induced ‘B’ to buy and pay for it. Afterwards the plot of land became the property of ‘A’. ‘A’ brought a suit to set aside the sale in favour of ‘B’ on the ground that, at the time of sale, he had no title. In such suit

This is an application of the doctrine of estoppel. 'A' intentionally misrepresented that he owned the land, inducing 'B' to purchase it from him. Later, when 'A' actually acquired title to the land, he sought to set aside the sale by claiming he had no title at the time of sale. The law will not allow 'A' to take advantage of his own fraud - he is estopped from denying the title he represented he had when he induced 'B' to buy. The principle is that a person cannot approbate and reprobate - cannot benefit from their own wrongdoing. Even though 'A' technically lacked title at sale time, equity prevents him from proving this to 'B's' detriment.