Political instability grips the UK as Health Secretary Wes Streeting resigns, calling for a leadership contest to replace Sir Keir Starmer. With bond markets already restive over UK public finances, this marks the fifth potential midterm prime minister change since 2016. UK's 10-year yield has been the highest in the G7 since Labour's October 2024 budget, raising investor concerns about fiscal sustainability amid political uncertainty.

Britain's long-term borrowing costs have climbed since the pandemic, fueled by wasteful spending, weak growth, and fiscal missteps like Liz Truss's disastrous "mini" budget. Political turbulence has exacerbated concerns, with 30-year government borrowing costs hitting their highest since 1998. Investors view Starmer and Chancellor Rachel Reeves as more trustworthy with public finances than potential successors like Andy Burnham or Angela Rayner, who favor bigger state spending.

The bond market acts as a critical check on UK fiscal policy amid political infighting. Britain already spends twice as much on debt interest as on defense, with higher yields pushing up mortgage rates. Political leaders blaming financiers reveal a naive grasp of finance—spending exceeds tax collection, requiring bond issuance. Investors logically demand higher rates when showing little sign of reducing expenditure or increasing revenues through growth measures.