Britain learns the price of a budget nobody believed

On Monday, 3 October, the chancellor dropped the planned abolition of the 45p top rate of income tax, a retreat forced by the market's punishing response to £45 billion of unfunded tax cuts. The climbdown was an attempt to restore discipline among Conservative MPs and to calm international bond markets. It will do neither job fully. The measure being reversed was worth barely £2 billion a year in revenue, and dropping it changes little in the underlying fiscal arithmetic. Britain has found that the bond vigilantes were never dead, merely waiting for a government careless enough to test them.

For decades, rich countries that borrow in their own currency have assumed their fiscal room was close to unlimited. The orthodoxy held that borrowing limits applied to emerging markets with foreign-currency debt, or to euro-area governments without a central bank of their own to lean on. The British experiment disposed of that belief in forty-eight hours. When a country running a current-account deficit of more than 5 per cent of GDP announces permanent, debt-funded tax cuts in the middle of an inflation shock, investors do not applaud its supply-side ambitions. They demand a higher risk premium, immediately.

Four weeks of self-harm

The package was the opening act of a government barely a month old. Liz Truss became prime minister on 6 September, and within days her chancellor, Kwasi Kwarteng, had dismissed the Treasury's most senior civil servant. On 23 September he cut the basic rate of income tax to 19p, cancelled the planned rise in corporation tax to 25 per cent and reversed the latest increase in national insurance, all without a forecast from the Office for Budget Responsibility. By 27 September the International Monetary Fund had publicly urged the government to reconsider, an unusual rebuke for a G7 economy.

How the premium bites

The risk premium works quickly. When international fund managers decide that a government's fiscal policy is fighting its own central bank, they sell its bonds as well as its currency. The falling exchange rate adds to imported inflation, which forces the central bank to signal steeper rate rises. That in turn raises the government's borrowing costs and widens the projected deficit.

The effect showed up at once in a sharp steepening of the gilt curve. Benchmark ten-year gilt yields rose past 4 per cent, and British mortgage lenders pulled more than forty per cent of their products within a week. Tax cuts meant to generate growth produced the opposite. They set off a credit squeeze across the banking system and raised borrowing costs for households and companies throughout the country.

Money markets did the rest. In the days after the statement, futures traders priced Bank Rate rising towards 6 per cent next year, from 2.25 per cent now, and lenders reprice fixed-rate mortgages off those swap rates, not off Bank Rate itself. A household whose two-year fix expires this winter is therefore borrowing at a rate set by the market's view of the government's credibility, before the Bank of England has moved at all.

The sums still don't add up

The U-turn on the 45p rate makes almost no difference to Britain's medium-term fiscal path. More than forty billion pounds of uncosted tax cuts remain, alongside an open-ended energy price guarantee likely to cost tens of billions over the winter. The guarantee caps a typical household's annual energy bill at £2,500 for two years from 1 October, so its cost moves with wholesale gas prices that the Treasury does not control. That leaves the Treasury with a large hole to fill. Filling it with heavy borrowing while the Bank of England is trying to squeeze out excess demand is a recipe for gilts to keep underperforming.

The rating agencies stir

The verdict has been formalised. On 30 September S&P Global kept Britain's AA credit rating but cut its outlook to negative, citing the unfunded tax cuts, and Moody's warned the same week that the package was negative for the country's credit standing. A downgrade would not stop Britain borrowing, since domestic pension funds and insurers must hold gilts whatever their rating. It would add one more reason for foreign holders, who own a large slice of the market, to ask for a higher yield.

Barber's ghost

The last British budget to cut taxes this heavily was Anthony Barber's in 1972, a dash for growth that ended with inflation above 20 per cent in 1975 and, the following year, a loan from the IMF. The parallel is imperfect, since the Bank of England now sets interest rates independently. But the Barber boom ran for a while partly because exchange controls kept British savings at home. Those controls went in 1979, and the verdict this time took days instead of years.

Households with mortgages pay first, as borrowers coming off cheap fixed-rate deals face quotes that have jumped within a fortnight, while savers are finally offered better deposit rates. The strongest case against this column is that the market has already calmed: sterling has recovered from its record low and long gilt yields have fallen back since the Bank of England intervened. That calm was bought with the Bank's balance sheet, and its emergency purchases are due to stop on 14 October, leaving the fiscal hole where it was.

What would restore trust

Three dates will decide whether the premium shrinks. The end of the Bank's gilt purchases on 14 October will show whether the market can stand without support. The Bank's next rate decision, on 3 November, will show how far it feels obliged to offset fiscal policy. And the medium-term plan with independent forecasts, promised for 23 November, will show whether the Treasury is prepared to cut spending or reverse more of the tax package to close the gap.

International investors now want something in return for continuing to lend. They want a return to fiscal orthodoxy, checked by independent forecasts from the Office for Budget Responsibility and backed by believable limits on spending. Until the chancellor publishes costed plans that the Office for Budget Responsibility can vouch for, gilt investors will keep charging Britain a premium, and households will feel it first in their mortgage rates. Britain has given the world a lesson in the limits of sovereign borrowing, and British taxpayers will be paying for it for years, starting with the borrowers who refinance this winter.