Possible Clues:

• Some actors in one Shakespearean part
• Gold shown by vice ring to Illyrian duke
• Duke of Illyria
• Mrs Radcliffe saw Illyrian duke as assassin?
• A duke, European or Chinese?
• A Shakespearean role covered by some actors in Oxford
• He loved Olivia but married Viola
• Twelfth Night duke
• He says 'If music be the food of love, play on'
• Speaker of Shakespeare's 'If music be the food of love, play on'