It was clear , he added , that Michael Mansfield QC , counsel for Mr al Fayed at the inquest , " wanted the Duke of Edinburgh to be called in order to cross-examine him whether he had expressed himself in such terms of hostility to Diana , Princess of Wales , that members of the SIS ( Secret Intelligence Service ) , without his knowledge , or the knowledge of those responsible for the service , conjured up a plot of their own to arrange for her to be killed . "