I can tell the hon. Gentleman what changed my mind, and I thank him for asking the question that I deliberately prompted. Hansard of 4 December 1978 quotes the then Secretary of State for Energy, the right hon. Member for Chesterfield as stating:
I have never found the NUM in any way unreasonable where closures are necessary because of exhaustion or because pits are out of line in economic terms."—[Official Report, 4 December 1978; Vol. 959, c. 1015–1016.]
I believe that that answers the hon. Gentleman's question.
Of paramount importance is a reduction in coal prices of 22 per cent. in real terms, representing a loss in sales realisations for British Coal of £900 million per year. Collieries continue to improve their performance. In Nottinghamshire, there is a big switch to retreat mining. This year, 52 miles of underground roadways will be completed. Leading the way are Thoresby and Rufford collieries, with record-breaking performances of 130 m per week. Bilsthorpe pit is about to begin a £10 million underground motorway 4,000 m long.