The FTSE 100 moved cautiously higher as investors responded to hopes that a US-Iran agreement could ease pressure on global energy markets and reduce inflation risks for businesses and households.

London stocks gained ground after reports that the United States and Iran had reached a preliminary deal to end more than 100 days of conflict in the Middle East. The prospect of the Strait of Hormuz reopening to commercial shipping has pushed oil prices lower and lifted sentiment across global markets.

However, the market reaction has been measured rather than euphoric. Investors are still waiting for more detail on the agreement, including how quickly shipping routes can normalise, whether sanctions relief will follow, and whether the deal will hold beyond its initial framework period.

For the UK economy, the issue is bigger than one day of market movement. The conflict has driven up energy prices, reshaped expectations for inflation, and complicated the outlook for interest rates. A sustained fall in oil and gas prices could ease pressure on consumers, businesses and the Bank of England. A fragile or limited deal could leave markets exposed to renewed volatility.

Relief rally meets caution

City AM reported that the FTSE 100 was inching up as investors weighed the latest developments in the US-Iran agreement. Brent crude was trading below $83 a barrel at the time, while Asian markets advanced cautiously.

The optimism followed a wider global market rally earlier in the week. Equity investors welcomed the possibility that Gulf oil exports could return more freely to global markets, reducing one of the main inflation threats hanging over the world economy.

But the cautious tone reflects the uncertainty that remains. The agreement is expected to create a 60-day framework for wider negotiations over Iran’s nuclear programme. Questions remain over the timing of the Strait of Hormuz reopening, the monitoring arrangements, and the wider security position in the region.

That matters because markets have been pricing in not only the conflict itself, but the risk that energy prices could stay higher for longer.

Oil prices drive the mood

Oil has been the central link between geopolitics and financial markets.

The Strait of Hormuz is one of the world’s most important oil and gas shipping routes. Any disruption can affect energy prices quickly, with knock-on effects for inflation, transport, manufacturing, consumer spending and central bank policy.

Brent crude fell sharply after hopes of a deal emerged, with Reuters reporting that prices later dropped below $80 a barrel as investors considered the possibility that Iranian oil could return more fully to global markets. Any additional Iranian supply would take time to materialise, and would depend on the durability of the agreement, but the direction of the price move has been enough to change market sentiment.

The impact is mixed across the FTSE 100.

Lower oil prices can weigh on energy companies such as BP and Shell, which are heavily represented in the London market. At the same time, they can help airlines, travel companies, logistics firms, retailers and consumer-facing businesses by reducing fuel and operating cost pressure.

That helps explain why the index reaction has been more nuanced than a simple rally. Falling oil is good news for inflation and many consumers, but it can reduce earnings expectations for some of the FTSE’s largest constituents.

Inflation pressure eases, but does not disappear

The fall in oil prices comes at a sensitive time for the UK.

Inflation unexpectedly held steady at 2.8% in May, unchanged from April’s 13-month low. That was better than economists had expected, but still above the Bank of England’s 2% target.

The energy shock has been one of the main reasons inflation concerns have returned. Higher oil and gas prices affect fuel, utility bills, shipping, food production and business costs. If firms pass those costs on to customers, inflation can become broader. If workers then seek higher wages to offset the squeeze on living standards, the Bank of England faces a more difficult policy challenge.

For now, markets appear to believe the US-Iran deal reduces the risk of a severe energy-driven inflation spiral. But central banks are unlikely to react to one week of price moves alone. Policymakers will want to see whether lower energy prices are sustained and whether they feed through into actual costs for households and firms.

Services inflation also remains a concern. While headline inflation was steady, services inflation rose to 3.7% in May. That matters because the Bank of England sees services inflation as a guide to domestic price pressure.

Bank of England in focus

The Bank of England is expected to keep interest rates on hold at 3.75% when it announces its latest decision. The easing in oil prices has reduced pressure for an immediate rate rise, but the central bank is unlikely to signal victory over inflation.

For investors, the language used by the Bank may matter more than the decision itself. A hold is widely expected. The important question is whether policymakers suggest rates could still rise later this year, or whether the fall in oil prices gives them more room to wait.

The market has already scaled back some expectations for further rate increases. That has helped risk assets, but the outlook remains data-dependent.

For businesses, a pause in rates would provide some stability, but not necessarily relief. Borrowing costs remain much higher than during the long period of ultra-low interest rates. Companies with floating-rate debt, refinancing needs or major investment plans are still operating in a more expensive funding environment.

Lower energy prices may help, but they do not automatically solve the wider cost and demand challenges facing UK businesses.

Sterling reaction muted

Currency markets have been more restrained than equity and oil markets.

Sterling held broadly steady against the US dollar as traders assessed the US-Iran agreement and looked ahead to UK inflation data and the Bank of England decision. That muted response suggests currency traders are waiting for clearer evidence that the deal will translate into a more stable energy and inflation outlook.

A lower oil price can support sterling indirectly if it improves the UK’s inflation and growth outlook. But if global investors continue to see uncertainty around UK policy, weak growth or political risk, the currency may not respond strongly.

For importers and exporters, the pound remains an important factor. A weaker sterling can increase import costs, adding to inflation pressure. A stronger sterling can help reduce imported inflation, but may make exports less competitive.

The current market picture is therefore one of cautious stabilisation rather than a decisive shift.

Winners and losers in the market

The business impact of the oil price fall will vary by sector.

Airlines, delivery firms, supermarkets, manufacturers and logistics companies may benefit if fuel and energy costs ease. Retailers and leisure businesses could gain if lower fuel bills support household disposable income.

Manufacturers may also welcome lower energy costs, particularly after months of concern that high industrial electricity and gas prices are damaging UK competitiveness. If energy costs fall and stay lower, it could improve margins and ease pressure on investment decisions.

But energy producers face the opposite dynamic. Lower oil prices can reduce revenue expectations and put pressure on share prices. That matters for the FTSE 100 because oil majors are large index constituents and important dividend payers.

There may also be implications for defence stocks. If investors believe geopolitical risks are easing, some conflict-linked premiums may reduce. But given the wider uncertainty in the Middle East, Ukraine and global security policy, any shift may be limited.

Markets want detail

The key issue now is detail.

Investors want to know whether the US-Iran agreement is a genuine turning point or a temporary pause. The most important questions include how quickly the Strait of Hormuz can operate normally, whether insurers and shipping companies will regain confidence, whether Iranian exports can increase, and whether the political agreement survives the next phase of talks.

Oil markets can move quickly on headlines, but physical supply chains take longer to normalise. Mines, ports, shipping routes, insurers, refiners and traders all need confidence before normal trade fully resumes.

That means the impact on the real economy may lag behind the market reaction.

If oil prices remain lower, the benefits could gradually feed through into transport, energy bills, inflation expectations and consumer confidence. If the deal falters, markets could quickly reverse.

A market rally built on relief, not certainty

The FTSE 100’s cautious gains reflect a broader market mood: relief that the worst energy-supply risks may be easing, but continued uncertainty over what comes next.

The immediate fall in oil prices is positive for many businesses and households. It reduces the risk of a further inflation shock and may give the Bank of England more room to avoid raising interest rates immediately.

However, the rally is built on expectations rather than confirmed long-term change. The agreement still needs to be signed, implemented and tested. Oil supplies still need to normalise. Central banks still need to see sustained progress on inflation.

For investors, this makes the current environment difficult to read. Markets may continue to rise if energy prices fall further and central banks sound more relaxed. But they remain vulnerable to renewed geopolitical tension, disappointing economic data or signs that inflation pressure is not fading as quickly as hoped.

For UK businesses, the practical message is similar. Lower oil prices are welcome, but planning should remain cautious. Energy, interest rates, currency movements and consumer confidence remain major variables.

The FTSE 100’s move higher is therefore not a sign that risk has disappeared. It is a sign that markets are beginning to price in the possibility that one of the biggest risks facing the global economy may finally be easing.