Only psychologically. From a political point of view, it would have been best for Britain to join the eurozone at the beginning, in 1999, when we could have tried to make the rules suit us better, have better claim to locate the European central bank, or to form a strategy for staying out permanently.

Today, the political argument is that after our rift with France and Germany over Iraq, opting for a referendum would mend fences while opting against would confirm the UK as being “semi-detached Europeans”. But the Commons Treasury Select Committee, while clearly divided on the main issue, has unanimously agreed that passing the Chancellor's five economic tests should be an essential condition of entry. From an economic point of view, some of the issues remain the same, whenever you choose, but some genuinely do change over time.

Proponents of entry argue, for instance, that the sharp fall of sterling against the euro this year, which has taken the single currency from 64p to 69p, provides a one-off opportunity to join after years when sterling was uncompetitively high. Some even argue that, if the exchange rate fell much lower, France and other existing members would block UK entry on the grounds that we would be too competitive.

But do not expect pro-euro campaigners to give up arguing for future entry if this "unique" chance is missed. Certainly 69p is a more realistic exchange rate to set for ever than the euro's nadir of less than 58p in 2000, but it is still lower than the 71p at which the euro started and, at the time, that was thought too high for it to be good for British business to join.

What is the cost of staying out of the European single currency for British business?

Two costs are fundamental. Having a different currency from your biggest trading partners creates a risk that your contracts or investments will be wrecked by a future change in the exchange rate. Global companies might avoid that risk, for instance, by investing in the Republic of Ireland rather than across the border in Northern Ireland.

Even if companies can hedge against short-term risks by using financial futures and options, that adds to their costs.

There is also always expense and inconvenience in having to change currencies, as travellers can confirm. This is a particularly aggravating nuisance for European multinationals such as Unilever. The third cost is more nebulous: the uncertainty over future planning and investment caused by waiting for a decision to be made. A "no" decision will never be accepted as final so, in one sense, the only final end to uncertainty is to join.

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