Letterboxes could fall silent on Saturday mornings, after the postal workers’ union appeared to accept a proposal from Royal Mail that would abandon its duty to deliver all letters six days a week. Royal Mail is required to deliver post from Monday to Saturday under the terms of the universal service obligation (USO) set down by an act of parliament in 2011. Amid a long-running industrial dispute with the financially struggling company, the Communication Workers Union (CWU) has so far opposed a £300m cost-cutting blueprint that would include scrapping most Saturday services. But the union appeared to concede last week that a complete six-day service is unaffordable. The change of heart comes as the 500-year-old company battles a £3.1bn takeover bid from its largest shareholder, the Czech billionaire Daniel Křetínský. Speaking at the CWU’s annual conference in Bournemouth last week, the union’s deputy general secretary, Martin Walsh, said: “The reality is, the USO as a six-day option is no longer financially viable. The challenges we face are so significant – probably the most challenging time in this union’s history, whether it’s the USO change, sale or possible takeover.” Royal Mail reported a £1bn loss last year, with bosses blaming strike...