Adam Nicolson focuses on the controversial work of whale hunters as he tries to understand why the population of the water-dwelling mammals was so drastically reduced in the 20th century. In the first of two programmes, the writer discovers how whaling was commercialised to supply a growing demand for products such as umbrella stays and oil-burning street lamps - before industrialisation took hold and the inventions of Norwegian Svend Foyn revolutionised the practice.