Back in the mists of time when I was a schoolboy studying geography I used to look at the map of the UK and ponder over the great black blobs which were the nation's industrial conurbations.

London was a huge dark mass. In the south there were small black smears like Bristol, Southampton, in the Midlands a dark stain for Birmingham, Coventry, Dudley, Wolverhampton, then Sheffield, Leeds, Newcastle, Gateshead and Tyneside, Glasgow and a smear for Cardiff.