As President Trump touches down in the UK, a post-Brexit trade deal is top of the agenda. And one of the most controversial issues is whether the nation will have to accept chemically washed American chicken as part of a deal. It's been banned in the EU for more than 20 years because of concerns that it masks poor hygiene practices in other parts of the supply chain. Dispatches goes undercover in a major US poultry processing plant to investigate, while reporter Kate Quilton meets whistle blowers and insiders who claim that the Trump administration's close relationship with the industry may mean that the worst is yet to come.