IN THE days since the London bombings much blame has been apportioned for the rise of Islamic extremism in Britain. But few have considered the damage done by textiles.

I don’t say that flippantly. When you look at the textile industry — and its mismanaged decline — it has left devastating tears in our social fabric, racial isolation and hatred across large swaths of America’s South and Britain’s North.

But let’s start here. The success of the northern mill towns came from the technology that made Britain the world centre of textile manufacturing in the Industrial Revolution. But by the middle of the past century other countries had caught up, and cities such as Bradford and Leeds responded by running their looms 24 hours a day. Because the indigenous workers were not prepared to do night shifts, Pakistanis and Bangladeshis were brought in. They settled, as immigrants usually do, in the poorest parts of town.

So far, so familiar — it is a story that has been told time and again in places such as the East End of London, the first port of call for the Huguenot silk spinners, then Eastern European Jews, now also the Bangladeshis.

Yet when the mills declined across Yorkshire and Lancashire there was not much else for the workers, white or brown, to do. So instead of the steady progression seen in big cities such as London, where immigrants get richer, and move on and up, in the mill towns most people were left stuck at bottom of the heap.

Their isolation persists to this day — when I travel from London to those northern cities it is the racial segregation I find the most foreign. And, as we know, unfamiliarity breeds contempt. I don’t think it any accident that three of the alleged suicide bombers came from these isolating conditions, rather than the thriving, cosmopolitan London they attacked.

Only those terrorists can answer for the horror that they inflicted, but there is a wider problem. I am not saying there would have been any point propping up a dying industry, but investment should have gone into retraining and re-thinking the purpose of northern workers, not letting bits of our national fabric rot.

Instead, as studies after the Bradford riots of 2001 showed, local council housing policy may have exacerbated the racial isolation in those deprived towns. This is Britain’s dirty linen.