Constructive Trust are based on the knowledge and conscience of the trustee. In Westdeutsche Landesbank v Islington, Lord Browne Wilkinson said the essence of trust is to police the good conscience of the defendant. It acts upon the following equitable maxim: That equity operates on the conscience of the owner of the legal interest and in the case of a trust that legal owner has the responsibility to ensure that the beneficial interests are not defeated. Therefore, it behoves him to ensure that the legal interest is not affected. The defendant must have knowledge of the factors which give rise to constructive trust. Example: Mohamed is queuing up at the till at Monoprix Supermarket, he has bought many goods and therefore his bills come to a little less than NLe 200. Mistakenly, the person working on the till is of the view that Mohamed has profile her NLe 300 Note, and so he gives him a change of NLe 100 because she was of the view that it was NLe 300 given to her. The question will be the obligation of Mohamed as to the NLe 100 he has received from her all under the mistaken belief that it was NLe 300 he gave to her. In good conscience, Mohamed is supposed not to keep the NLe 100, but to give it back to the till operator as monies mistakenly given to him. The important point at which the court comes in is when did Mohamed realised that he has received NLe 100 that he ought not to have received. Summarize this text in fewer sentences