The yield on UK 30-year government bonds, or gilts, has climbed to its highest level since 1998, reaching 5.79% before settling near 5.6%. The 10-year yield also spiked close to 5.12%, an 18-year high, reflecting a sharp loss of investor confidence in British debt.
Bond yields rise when prices fall, signaling that investors demand a higher premium to hold UK debt. The primary driver is concern the Bank of England will keep interest rates high to combat persistent inflation, exacerbated by surging energy prices linked to the Iran war.
Beyond global factors, domestic political uncertainty is fueling the sell-off. Prime Minister Keir Starmer faces mounting pressure from his party's left flank, disarray over the Peter Mandelson Washington appointment, and a potentially devastating local election result. Over 5,000 council seats are up for grabs, and analysts predict Labour could lose more than 1,000 seats.
Investors fear a poor showing could trigger Starmer's ouster, with successors like Angela Rayner or Andy Burnham seen as favoring higher borrowing and spending, which would push yields even higher. According to Dan Coatsworth of AJ Bell, "There is a real risk of gilt yields soaring if Labour experiences a wipeout."
The cost to the Treasury is immense: every 0.25% rise in borrowing costs adds £2.5 billion annually to debt servicing. Already, a 0.5% increase this spring means an extra £5 billion per year. These higher yields translate directly into more expensive mortgages and corporate loans, potentially slowing economic growth and squeezing household incomes.