In 2024, Keir Starmer won one of the biggest election victories in modern British history. His party took a 174-seat majority.
On Monday, less than two years later, he stood outside 10 Downing Street and quit.
For investors, the drama isn't in the politics. It's in the bond market.
Starmer's government never recovered its early footing. It took heavy losses in May's local elections.
His own lawmakers turned on him over spending and welfare plans. Voters had soured on him, and so had much of his own party.
A poll last week showed 52% of Britons thought he should stand down.
That was up five points from May. The final blow came on June 18.
Andy Burnham, the former mayor of Greater Manchester, won a special election. He now looks set to take over, with backing from senior party figures.
That makes Burnham the UK's seventh leader in 10 years. Downing Street has become a revolving door.
His approval had slid for months. Finance minister Rachel Reeves faced the same fight over spending that wore the government down.
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The pound dipped on the news but didn't crater. The bigger worry sits in UK government bonds, known as gilts.
A gilt's yield is the interest rate the government pays to borrow. That yield jumped on Friday, right after Burnham's win.
It spooked investors for a reason. The UK already has the highest borrowing costs in the G7, the group of large rich economies.
The concern isn't Starmer leaving. It's what a Burnham government would do with spending and debt.
Would he spend more? Would he borrow more? No one knows yet.
As one economist put it, the market now has to price in a Burnham win. Under Starmer, the economy grew about 1.5%.
Markets remember the last time a UK leader spooked them. In 2022, Liz Truss lasted just 50 days after a tax-cut plan sent yields soaring and the pound lower.
Burnham once said the UK was too "in hock" to bond markets. Lately he's walked that back to calm investors.
Starmer's exit comes almost 10 years after Britain voted to leave the EU. No leader since has held the job for long.
Burnham has been trying to calm markets. He's softened past comments about not bowing to bond investors.
Whether that calm holds is the thing to track. He's also expected to put himself forward within weeks.
If no one runs against him, the contest could end fast. Traders will watch every word he says on tax and spending.
Markets hate surprises, and a new leader with new plans is a big one. The vote that matters next won't happen at the ballot box.
It'll happen in the bond market.
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