“I am most anxious that, in recognising this defence [of change of position] to actions of restitution, nothing should be said at this stage to inhibit the development of the defence on a case by case basis, in the usual way. It is, of course, plain that the defence is not open to one who has changed his position in bad faith, as where the defendant has paid away the money with knowledge of the facts entitling the plaintiff to restitution; and it is commonly accepted that the defence should not be open to a wrongdoer”
“[t]here is no room for the exercise of any discretion by the court in favour of one party or the other. If the recipient’s actions of changing position are treated here as illegal, the court cannot take them into account. The recipient cannot put up a tainted claim to retention against the victim’s untainted claim for restitution”
“However, the precise nature of this sufficient connection is elusive. It is best understood, at least where D’s conduct consists of assistance, as meaning that D’s conduct has made a contribution to the commission of the offence.””