UK gilt yields 2025 have climbed to levels not seen since June 2008, as US military strikes on Iranian oil tankers send crude prices sharply higher and amplify inflation fears across global bond markets. The 10-year gilt yield rose 4 basis points to 5.268% at the open, while the 30-year yield added 5 basis points to approach 5.89%, close to the previous session’s peak.
How the Strait of Hormuz Is Driving UK Gilt Yields 2025 Higher
The proximate cause is military, not fiscal. ABC News reported that US CENTCOM forces permanently disabled two Iranian oil tankers and destroyed a third after Iran’s Islamic Revolutionary Guard Corps launched ballistic missiles toward an American aircraft carrier and destroyer. Neither US vessel was struck and no personnel were injured. CENTCOM described the three tankers as part of a multibillion-dollar shadow network funding the IRGC and its regional proxies.
CBC News reported oil prices surged more than $4 a barrel on the news, settling at a five-week high after two tankers were hit while leaving the strait. Joel Kruger, market strategist at LMAX Group, characterised oil as having extended to a six-week high in early trading, with the renewed US-Iran escalation the dominant theme at market open.
The concern is not just today’s price move. According to a Congressional Research Service report, roughly 25% of the world’s maritime trade in crude oil and petroleum products passes through the Strait of Hormuz, along with roughly 19% of global liquefied natural gas. Iran’s IRGC has stated that US strikes would ‘tighten the lock’ on the strait. Any sustained closure, or even a credible threat of one, would feed directly into the inflation expectations that bond markets are now pricing.
The Fiscal Arithmetic Behind the Gilt Sell-Off
For the Andy Burnham government, the timing is punishing. Chancellor John Healey is navigating an autumn budget with shrinking fiscal headroom, and every sustained move higher in yields erodes it further.
The scale of that erosion is not abstract. When Reuters reported on the January 2025 gilt sell-off, Deutsche Bank chief UK economist Sanjay Raja estimated that the rise in yields at that time, if sustained, would add around £10 billion a year to Britain’s annual debt interest bill compared with the Office for Budget Responsibility’s October 2024 forecast. Raja warned the fiscal outlook implied ‘spending cuts, more borrowing, and likely a little more taxation.’ That was when 10-year yields were at 4.821%. They are now materially higher.
The volume of debt the government needs to place makes the yield environment consequential. The UK Debt Management Office’s Debt Management Report 2025-26 sets planned total gilt issuance at £299.2 billion for the financial year. Short conventional gilts account for 37.1% of that figure, medium conventional gilts 30.0%, long conventional gilts 13.4%, and index-linked gilts 10.3%. With that much paper to sell, every basis point of additional yield is a budget line that writes itself.
There is at least one piece of evidence that demand has not collapsed. Bloomberg reported that a recent 10-year gilt syndication attracted £148 billion of investor orders, a record for any such sale, at a yield of 4.9158%, the highest for a 10-year gilt sale since 2008. Yield hunters are clearly present. The question is at what price they stay.
The January 2025 episode offers a useful reference point. Thirty-year gilt yields reached 5.383% then, the highest since August 1998, in what Reuters described as the biggest daily price fall in nine months at that time. Current 30-year yields at 5.89% have now moved well past that watermark.
The next test is simple: does the Hormuz situation stabilise, or does a sustained oil shock force central banks to hold rates higher for longer than markets had assumed? If it is the latter, the October budget’s fiscal arithmetic will need rewriting before the ink is dry.
