When police in England raided a fentanyl lab outside the northern city of Leeds in early 2017, the bust sent shockwaves across the country.

The raid and subsequent conviction of three men – who made and sold around £164,000 worth of the opioid in five months – was the first major fentanyl case in Britain and it prompted dire warnings from law enforcement officers, health officials and the media that the U.K. was headed for a U.S.-style fentanyl crisis.