"Arnold Tustin is best known for his contributions to control theory and its application to electrical machines. However, his interests were much wider than electrical engineering, for he was a polymath who brought a systems approach to each of the many areas that he investigated. In the modern jargon he thought ‘outside the box’ and in doing so championed the use of control systems theory beyond its traditional limits. His impact was such that, in addition to his engineering contributions, he is well known for his systems treatment of economics and to a lesser extent... biology."