Urban sites and the stratigraphic revolution in archaeology

The lead article in this forum, ‘The challenges and opportunities for mega-infrastructure projects and archaeology’, by J. J. Carver, brought a couple of London incidents to mind, the two separated by slightly more than a generation, but each pertaining to the challenges of ‘urban’, or rather any ‘mega-stratified’ sites, for the dense stratification in many contexts is but the result of minor and mega infrastructure projects of the Past.