Combined with nylon (a Du Pont invention from 1939), Spandex allowed the production of tights with no garter or stocking belt, which in turn meant designers like Mary Quant could take the hemline of the skirt way up.
She opened the coat, got back down on her knees, and with one hand yanked the skirt of the coat up behind her, folded over on itself, so that it was out of the way.