Mr Mansfield is acting on behalf of Dodi's father, Mohamed Fayed, who has repeatedly claimed that the Queen's husband worked with MI6, the intelligence service, to have Diana and his son murdered in Paris. Prince Philip ridicules the notion but knows that should he be called to the witness box, even denials to questions such as "Did you want Diana dead?" or "Did you work with the intelligence service to have the princess murdered?" would result in sensational headlines around the world