Dame Anna Wintour had just sent off her first edition of US Vogue in October 1988 when the magazine received a phone call from the printers. They had seen the issue's front cover, and had one question: "Has there been a mistake?"

The cover, Dame Anna's first as editor-in-chief, featured a lesser-known model, Michaela Bercu, smiling at the camera in a stylish Christian Lacroix couture jacket.

But two things were notably different from usual: the model was standing outside, in the street, and wearing a pair of jeans. The printers half-assumed there had been some kind of error.

"I couldn't blame them," Dame Anna later recalled. "It was so unlike the studied and elegant close-ups that were typical of Vogue's covers back then, with tons of makeup and major jewellery. This one broke all the rules."

The jeans had, in fact, been a last-minute addition, after the skirt which Bercu was supposed to wear didn't fit properly. But the intended message was clear: the cover star was a regular, everyday girl - and this was a new era for Vogue.