Rishi Sunak officially becomes U.K. prime minister

• At 42, Sunak is also the youngest prime minister to be appointed since 1812.

What he's saying: "Right now, our country is facing a profound economic crisis. The aftermath of COVID still lingers. Putin's war in Ukraine has destabilized energy markets and supply chains the world over," Sunak said outside 10 Downing Street.

• Truss "was not wrong to want to improve growth in this country ... but some mistakes were made," he added. "I will place economic stability and confidence at the heart of this government's agenda. This will mean difficult decisions to come."

How it happened: Former Prime Minister Boris Johnson announced a surprise bid to return to Downing Street but dropped out Sunday after falling well behind Sunak, his former finance minister (he claimed to have 100 backers, but was well short of that number in the public tally).

• House of Commons leader Penny Mordaunt dropped out minutes before the deadline, rendering the planned online vote among party members unnecessary.

Flashback: Sunak also led among MPs during the previous leadership race, but party members ultimately opted for Truss. Sunak warned presciently at the time that Truss' tax cuts would force a spike in interest rates.

State of play: Sunak is perhaps best known for implementing the U.K.'s economic support package during the pandemic. He helped push Johnson out of office by resigning from his Cabinet in July.