Look down on the pavement in any older, wealthier part of London and you may see these ever-varying cast iron covers. Locked from the inside, they cover a chute used to drop coal into cellars, from where it would be hauled to fireplaces by scullery maids. With every room in the house having a coal fire, cleaning coal dust was eternal work. Read more at http://wp.me/pQO2b-1y