British PM’s 1st day at 10 Downing St. will stretch from nuclear weapons briefing to Larry the cat

LONDON — After a few hours of sleep to shake off a night of celebration and an audience with the king, Keir Starmer stepped through the front door of 10 Downing St. for the first time as prime minister on Friday. “I’ve often mused over the fact that no one really claps you on the way out whenever you leave your job,’’ she said during a briefing about the first days of a new administration Nuclear trigger One of the most sobering moments of any prime minister’s first day on the job is the realization that he now has the ultimate authority over whether to launch Britain’s nuclear missiles. In the U.K., this is underscored when the country’s top civil servant informs the new prime minister that he has to write “last resort letters” to the captains of Britain’s four nuclear-armed submarines telling them what to do in the event of a nuclear attack that wipes out the civilian leadership. 10 Downing St. is as much of a shorthand for Britain’s prime minister as the White House is for the U.S. president. “No major corporation – or indeed government department – operates from a largely unreconstructed 300-year-old building or has the CEO living above the shop.” One of the first decisions Britain’s new prime minister will have to make is whether to live in the two-bedroom apartment above 10 Downing St., traditionally the home of Britain’s leaders, or the more spacious four-bedroom apartment over No.