As Chairman of the NCB, Robens oversaw substantial cuts in the mining industry, many of them reflecting market forces and government policies originated before he assumed the post. Although he lobbied to protect the industry, his reputation as a socialist necessarily suffered: when he took over as NCB chair there were 698 pits employing 583,000 miners, but by the time he left the post ten years later there were only 292 pits employing 283,000 miners. For a while Robens had a constructive working relationship with miners' leader Will Paynter, but he had a combative relationship with the Wilson Labour government. Industrial relations deteriorated during his tenure, and there was an unofficial strike in 1969 that lost £15 million and 2.5 million tonnes of coal as a result of a walkout by 140 of the 307 NCB collieries.