It happened during the 1990s according to https://www.cntraveler.com/stories/2016-04-22/how-london-became-one-of-the-best-food-cities-in-the-world https://www.c

It happened during the 1990s according to https://www.cntraveler.com/stories/2016-04-22/how-london-became-one-of-the-best-food-cities-in-the-world https://www.cntraveler.com/stories/2016-04-22/how-london-bec..., though when I visited in 1998 it was still notorious in Americans' minds for plain, boring food.