Mortgage rates in Britain are climbing again, and the reason has little to do with the Bank of England. Bank Rate has sat at 3.75 per cent since December 2025, yet the average two-year fixed rate rose in early August for the first time since April. The cause sits 3,000 miles away, in a stand-off between Washington and Tehran that has kept the Strait of Hormuz shut and oil above where it began the year. Higher oil feeds Inflation expectations, which feed bond yields, which feed swap rates — and swap rates set the price of a fixed-rate mortgage. The chain is real. In Britain, though, it is weaker than in the United States.

What the stand-off has done to the oil price

Since US and Israeli strikes on Iran in late February 2026, the Strait of Hormuz — which normally carries a fifth of global seaborne oil — has been largely closed. Brent spiked to around $126 a barrel in mid-March, retreated after a US-Iran memorandum of understanding in June, then jumped after renewed US strikes in July.

In mid-August, Brent traded around $84, up roughly 16 per cent since the conflict began. Traffic through the strait had collapsed to eight to fifteen vessels a day, against about 130 before the war. A risk premium remains embedded.

From Crude Oil to your mortgage: how the chain works

Central banks do not set fixed Mortgage rates. Fixed rates are priced off Interest Rate swaps — contracts banks use to exchange a floating rate for a fixed one, letting them lend for five years without risking a move in funding costs. Swap rates track expectations of where policy rates will sit over that period, which track government bond yields.

Oil enters at the top. Higher crude raises transport and Manufacturing costs and, in the UK, feeds through wholesale gas into household bills. Investors mark up inflation expectations, Demand a higher yield to lend to governments, and swap rates follow. Lenders reprice within days, because a fixed-rate offer left on the shelf while funding costs rise loses them money.

Where UK borrowing costs stand now

UK swap rates on 14 August 2026 stood at 4.14 per cent for two years and 4.24 per cent for five — both well above Bank Rate, which tells you markets are not pricing near-term cuts. The ten-year gilt yield was around 4.9 per cent, up a third of a point over the year.

Moneyfacts data put the average two-year fixed rate at 5.63 per cent and the five-year at 5.66 per cent at the start of August, up 0.12 percentage points on the month — the first increase since April. Average deal shelf life compressed to 11 days from 14. Santander and Halifax raised selected fixed rates by up to 0.19 and 0.20 points, while Nationwide and Coventry cut some — the market is not moving in one direction.

The UK move is smaller than America’s — and that matters

In the United States, Freddie Mac’s survey showed the 30-year fixed rate at 6.69 per cent in mid-August, its fifth consecutive weekly rise, and the 15-year at 6.01 per cent — both above year-ago levels. US mortgage rates track long-dated Treasury yields directly, so an inflation scare transmits fast.

Euro-area markets moved too: the German ten-year Bund yield reached around 3.16 per cent in late July and the two-year 2.79 per cent, its highest since early 2024, with French and Italian yields following.

Britain’s picture differs in timing rather than direction. The violent part of the UK move happened in the spring, when ten-year gilt yields briefly pushed above 5 per cent in late April — a level last seen in 2008 — before retracing. The August increase in UK mortgage pricing is a twelve-basis-point drift, not a lurch. Anyone claiming the Iran crisis has just repriced the British mortgage market is overstating it. UK rates have stopped falling rather than jumped.

The refinancing wall behind the numbers

Around 750,000 UK households on fixed rates below 3 per cent see those deals expire during 2026, facing an average monthly payment rise of roughly £170, according to Bank of England analysis. The Bank estimates more than five million homeowners will see repayments rise by the end of 2028. For them, whether the average two-year fix is 5.5 or 5.7 per cent matters far less than the gap between 2.5 and 5.6.

Money and Credit data for June showed the effective rate on newly drawn mortgages climbing to 4.35 per cent, with net mortgage borrowing jumping to £7.7bn as borrowers rushed to lock in.

What this is doing to house prices

House prices are flat rather than falling. Nationwide’s July index showed annual growth of 1.8 per cent, down from 2.2 per cent in June, with the average price at £277,542. The Lloyds index put annual growth at just 0.1 per cent. The official UK House Price Index, based on completed Land Registry sales, recorded 2.7 per cent growth in May — official data lags.

Rightmove reported asking prices falling 1.0 per cent in July, the steepest July decline in a decade, with Supply near twelve-year highs.

The risks from here

The obvious risk is re-escalation. The Bank of England’s July Financial Stability Report warned that renewed conflict could trigger “further Volatility and sharp upward repricing in energy markets”. Ofgem’s price cap rose 13 per cent from 1 July, and CPI inflation — 2.6 per cent in June — is expected by the Bank to peak above 3 per cent this year. Three of nine MPC members voted in July for a rise to 4 per cent. A hike is not the central case, but no longer a fringe view.

What could change the picture

A credible Hormuz agreement would do most of the work. If shipping normalises, the risk premium in crude unwinds, inflation expectations fall, swaps follow and fixed mortgage rates ease. Absent that, expect rates to grind sideways through the autumn. The next MPC decision comes on 17 September, and forecasts assuming autumn cuts look increasingly optimistic.

A squeeze that never quite ended

UK mortgage costs have stopped improving rather than deteriorated sharply. The Iran stand-off is the proximate cause: it has kept oil elevated, inflation expectations sticky and the Bank of England immobile. But transmission into UK pricing has been modest, and smaller than moves in US mortgage rates and euro-area bond yields. For the three-quarters of a million households rolling off sub-3 per cent deals this year, that distinction is academic. Their payments are going up either way.