HARDTOP HISTORY: Asphalt is a bitumen-and-aggregate carpeting that’s so ubiquitous it’s invisible. Blacktop has a long history but there was no inevitability about its mainstream adoption. It took many years of trial and error before the modern recipe was settled upon. In the meantime, many roads were capped with granite setts, dusty macadam and forgiving rubber. London’s roads, like that of many other cities, were surfaced with Australian hardwoods.