LONDON—A year to the day after they were first ordered to stay at home to contain the spread of COVID-19, Britons will remember the more than 126,000 people who have lost their lives to the virus, a toll few could have imagined in March 2020. People were being invited to observe a minute’s silence at midday (1200 GMT) to honour the dead, and to stand on their doorsteps at 8 p.m. holding candles or torches. Official data shows that on March 23, 2020, when Prime Minister Boris Johnson stunned the nation by ordering people to stay at home and by shutting down much of the economy, fewer than 1,000 Britons had succumbed to the novel coronavirus. Now, the number of people known to have died in the United Kingdom within 28 days of testing positive for COVID-19 stands at 126,172—the worst toll in Europe and fifth highest in the world. …