The UK's government borrowing costs have breached the crucial 5% mark, a threshold last seen during the tumultuous Iran conflict era. This significant increase is directly linked to the catastrophic collapse of a fragile ceasefire between Iran and the US, which has sent shockwaves through global energy markets and fuelled inflation fears. The yield on the UK's 10-year government bond – a key indicator of long-term borrowing capacity – surged by as much as seven basis points on Tuesday morning, as tensions in the Middle East intensified.
The breakdown of the ceasefire saw both the US and Iran exchange military strikes for a third consecutive night, precipitating a sharp rise in global oil prices. Brent crude, the international benchmark, leapt by over 9% in a single session on Monday, reaching levels not witnessed since mid-June. The US military confirmed further offensive actions against Iranian sites, stating their intent to continue imposing costs on Iranian forces and degrade their capacity to target commercial shipping. Concurrently, former US President Donald Trump reinstated a blockade of Iranian vessels in the Strait of Hormuz, while the UAE reported two tankers were struck by Iranian missiles.
This renewed instability has had a profound impact on UK financial markets. Analysts attribute the pronounced sell-off in UK gilts to the country's substantial reliance on imported energy and persistent underlying inflation. When inflation is high or expected to rise, bond traders typically demand higher interest rates to compensate for the erosion of real returns. Investors are also factoring in the likelihood of central banks maintaining higher interest rates for a longer period to combat stubborn price increases. Daniel Mahoney, a senior UK economist at Handelsbanken, noted the exceptional volatility in UK gilts since the war began, predicting that UK yields could remain the highest in the G7.
The impact extended to Britain's shorter-dated bonds, which are more sensitive to immediate interest rate expectations. The yield on the two-year gilt rose by 10 basis points, trading above 4.5% for the first time since mid-May. This movement reflects increased market anticipation that the Bank of England may raise its central interest rate at its next meeting on 30 July. Financial markets are now pricing in a full interest rate hike from the Bank of England by the end of the year, with similar expectations for rate increases by the US Federal Reserve.
For the incoming Prime Minister, Andy Burnham, this sharp rise in borrowing costs presents an immediate and substantial fiscal challenge. The 60-day ceasefire agreed in June had offered a brief respite, with the 10-year bond yield falling from its May peak. However, the renewed energy price spike and subsequent inflationary pressures mean that the government will face higher costs for servicing its debt, potentially impacting public finances just as it takes office.