Philippa Gregory said this quote

Say yes,’ he whispers. ‘Marry me.’I hesitate. I open my eyes. ‘You will get my fortune,’ I remark. ‘When I marry you, everything I have becomes yours. Just as George has everything that belongs to Isabel.’‘That’s why you can trust me to win it for you,’ he says simply. ‘When your interests and mine are the same, you can be certain that I will care for you as for myself. You will be my own. You will find that I care for my own.’‘You will be true to me?’‘Loyalty is my motto. When I give my word, you can trust me.