In Markel International Insurance Company v Timothy Higgins, QBE Insurance (Europe) and another v Timothy Higgins [2009] EWCA Civ 790, the Court of Appeal held that the High Court Judge was correct in his finding that the defendant, Mr Higgins, an underwriting agent who suffered from Alzheimer's disease, had either conspired with others to defraud Markel and QBE (his principals) or that he had given dishonest assistance to others in breach of his fiduciary duty to Markel/QBE. The Court of Appeal found that the components of the fraud/dishonest assistance case brought against Mr Higgins were cumulatively overwhelming. In the circumstances, it was no defence that Mr Higgins's dishonest actions could be excused by intermittent forgetfulness (which was caused by his Alzheimer's) as Mr Higgins, must have known what he was doing (for example, consistently writing bonds over the prescribed limits set by Markel and QBE). Mr Higgins's appeal was therefore dismissed.

This case shows that the courts will not necessarily be receptive to a defence of mental illness where the evidence of dishonesty is overwhelming.