But this has happened only once , to John Erskine , 6th Earl of Mar who was deprived of both the knighthood and the earldom after taking part in the Jacobite rising of 1715 . The only individual to have suffered such a fate was John Erskine , 6th Earl of Mar who lost both the knighthood and the earldom after participating in the Jacobite rising of 1715 .