 There followed collaborative work on labour movements and labour history in other parts of Africa.However, his interest and expertise in labour developed into a wider project about the continuing significance of the movement of people across national boundaries and the problems to which this has given rise in very many parts of the world.In "The new Helots" (1987), he suggested that Marx had underestimated the continuing salience of migrant labour, a feature that allowed capitalism to thrive and thereby evade the fundamental confrontation between worker and employer that Marx predicted.