The Bank of England looks set to step into the unknown on Thursday, when it is expected to raise interest rates for the first time since 2007 at a time when growth appears weaker than before any other rate rise of the past 20 years.
Having cut rates to a record low 0.25% in August 2016 after Britons voted to leave the European Union, the Bank is now correcting course and falling in line with the US Federal Reserve and the European Central Bank, which are either raising rates or scaling back stimulus.
Whereas the United States and the eurozone are enjoying robust growth, however, Britain's economy has grown at its slowest pace in more than four years over the past 12 months.
Quarterly growth of 0.4 percent offers the weakest backdrop to any rate rise since the Bank became independent in 1997.
Britain's economy has grown at its slowest pace in more than four years over the past 12 months
True, inflation is at a five-year high of 3%, a full percentage point above the Bank's target, but that is mainly because the pound is an average 11% weaker against the currencies of Britain's main trading partners since the Brexit vote.
The bank has often overlooked past spikes in inflation if they were caused by currency fluctuations that were deemed to be temporary.
Inflation is set to fall this time too, but only slowly, as the bank judges domestic inflation pressures are pending.
Partly due to stagnant productivity since the 2008 financial crisis - and partly due to concerns about the effect of Brexit on immigration, trade and investment - BoE Governor Mark Carney thinks the economy cannot grow as fast as it has in the past without generating excess inflation.
"We're in a new paradigm," says George Buckley, an economist at Nomura who was one of the first to sense a change at the central bank earlier this year, when most economists were saying they did not expect rates to rise until 2019.
Raising rates now would be the biggest call on monetary policy Carney has made as governor, and may shape his legacy.
Carney has faced criticism from economists who say his past guidance on monetary policy has been unhelpful, and from Brexit supporters who say he is too focused on the risks of leaving the EU. But until recently his broad approach to interest rates has been fairly uncontroversial.
For most BoE watchers, the likelihood of a rate rise only became clear in September, when minutes of the nine-member Monetary Policy Committee's meeting that month showed underlying price pressures were no longer a minority concern.
Two policymakers voted for a rate rise, and a majority of the others said they expected to do so "over the coming months".
Almost all economists polled by Reuters last week expect the bank to raise interest rates to 0.5% from 0.25% on Thursday. Most do not expect another one next year and 70% said even one rate rise would be a mistake. The latter view is common in markets, too.
The bank says its policy decisions are not driven by exchange rates. When Carney gives his news conference at 1230 GMT on Thursday, he is likely to focus on a 42-year low in unemployment and how it heralds more upward pressure on wages and inflation.
Markets have priced in an almost 90% chance of a rate rise on Thursday, but then expect the bank to wait until late 2018 before raising again, Nomura's Buckley said.
Economists do not expect one or two rate rises will hurt growth much unless businesses or the public think many more will come and curb spending as a result.