Online giant Amazon has been accused of placing managers in its UK warehouses under such pressure some have suffered breakdowns. In an open letter to bosses, a group claims a “crisis” has led to them having to work more than 60 hour weeks, despite contracts stating they do 40 hours. It says: “This sustained pressure is having a severe and measurable impact on our mental health. Several members of our group have personally experienced stress-related issues, and we have witnessed colleagues break