As Britain lays the groundwork for a trade deal with America, chicken has become a bone of contention. The United States is likely to insist that its chlorine-washed poultry is part of any deal. Yet in a letter to the environment secretary, Theresa Villiers, environmental campaigners and Britain’s largest farming union have demanded “cast-iron” legal guarantees that a ban on chlorinated chicken would remain after Brexit. Mrs Villiers has meanwhile said that Britain would “hold the line” against the introduction of chlorinated chicken and hormone-treated beef into Britain, echoing the sentiments of her predecessor, Michael Gove. Yet such moves would be shortsighted.

A portion of US chicken is washed in chlorine or other antimicrobial substances to kill off salmonella, E coli and campylobacter, all bacteria