Labour leader Keir Starmer will officially become the UK's prime minister, leading his party back to government less than five years after it suffered its worst defeat in almost a century. For Starmer, it's a massive triumph that will bring huge challenges, as he faces a weary electorate impatient for change against a gloomy backdrop of economic malaise, mounting distrust in institutions and a fraying social fabric. (AP video/Kwiyeon Ha)