LONDON — Negotiations are finally underway for Keir Starmer's much-hyped Brexit reset. Expect to relive some trauma. Six months ago, the British prime minister came to a “common understanding” with the EU at an all-smiles summit in London. The two sides — keen to move on from years of bad blood over Britain's 2016 exit from the bloc — vowed to smooth trade in food and electricity. They'd make it easier for young people to live abroad, link their carbon markets, and cooperate more closely on