There must be an election coming up, for this was a "do nothing to upset people" Budget. Look at tax: no change in income tax or VAT; freeze or just index most duties on alcohol, petrol and tobacco; no significant changes in company taxation; the odd tax loophole closed but almost certainly new ones opened.

There must be an election coming up, for this was a "do nothing to upset people" Budget. Look at tax: no change in income tax or VAT; freeze or just index most duties on alcohol, petrol and tobacco; no significant changes in company taxation; the odd tax loophole closed but almost certainly new ones opened.

The message is the same on the spending side. Key areas such as health and education are protected; frontline services are boosted as bureaucrats are squeezed; overall spending is to rise in line with economic growth. And as for growth, thanks to the Chancellor's excellent stewardship, Britain has faster growth than the eurozone, Japan and the US.

But has this not been at the cost of a surge in borrowing? Well, yes, the Chancellor would argue, borrowing has risen, but Britain also has the lowest overall national debt of any of the Group of Seven developed nations. Further, the current deficit of 3.4 per cent of GDP is only a bit above the EU's Stability and Growth Pact's ceiling - which in any case, Gordon Brown argues, is not nearly as well-constructed as our own fiscal rules.

Put like that, it's all fine - except that it isn't. There is no catastrophe here. The economy is undeniably performing pretty well and Tories are wrong to suggest that there is a sword of Damocles hanging over the Government's finances in the shape of huge borrowings that we will all have shortly to pay back. We have such a folk memory of past economic failures that after a few good years it is hard to believe that things are coming right. But things are not quite as happy as they seem. This was Mr Brown's eighth Budget and inevitably the next four years are not going to be quite as easy as the ones to date.

Here's why. Start with the economy. It did indeed grow decently last year, by 2.3 per cent, and may well exceed 3 per cent this year. There is a general world recovery taking place and we should get some uplift from that. But we jolly well ought to be growing all right, for the UK has been given the largest fiscal and monetary boost of any large economy bar the US. Between 2000 and 2003, interest rates were cut by 3 per cent and fiscal policy was loosened by 3.25 per cent.

Part of price is higher public borrowing, with the projected total for the coming financial year (starting on 5 April) up another billion on last December's. Yes, it is only a billion, but in that phrase attributed to the US Senator Everett Dirksen, "a billion here, a billion there and pretty soon you're talking real money".

Another part of the price is higher personal borrowing: the chilling statistic is that Britons have borrowed three-quarters of all Europe's credit card debt. Sure, European individuals, unlike their governments, are a bit wimpish when it comes to borrowing, but it cannot be wise for us to be carrying quite such a large credit burden. And yet another part of the price is a current account deficit of more than 2 per cent of GDP.

This leads to a genuine puzzle. If the economy is indeed growing so well, why have tax revenues fallen short of Treasury projections? The Government has repeatedly missed its borrowing forecast not because of slow growth, or unplanned spending, but because something seems to be going wrong on the revenue side. At the moment those budget deficits are projected to inch downwards but if taxes keep coming in below target, they will head up and Mr Brown's golden rule will be for the birds.

Of course if the Treasury is right and growth this year is above 3 per cent, he can roll the debts forward for one more year. Then there will be an election and it will be someone else's problem. But even on his own figures there is a hint of slightly cooler times ahead.

One of the characteristics of Brown Budgets is that the glitz is in the speech and the nasties are in the detailed documents. But even in the speech there was a hint of menace as far as public spending was concerned.

First, overall spending will only rise at the same rate as the growth of the economy, 2.5 to 2.75 per cent. But public spending is labour intensive and wages will rise by more than that.

Just to stay in the same place there will have to be increased efficiency. That pressure is compounded by the specific demand that resources should be switched from those central functions to the front line. In principle that may be fine, but in practice it will be tough. A lot of people will made to feel uncomfortable and when public-sector unions face disgruntled members, ructions result. After the boom in spending of the past three or four years, the public sector faces much tougher times.

So too do the rest of us. A quick burrow into the documents shows that household consumption is forecast to grow more slowly in the future than it has in the past. Consumption has been growing at about 4 per cent a year, faster than the growth of the economy and increasing from less than 62 per cent of GDP in 1997 to nearly 66 per cent in 2004. It cannot carry on like this for ever and the Treasury has pencilled in consumption rising at only 2.5 per cent this year and next.

Gradually we will have to get used to coping with all that credit-card debt by increasing our living standards more slowly. We have had the seven fat years and while the next seven may not be that lean, they will feel that way.

The most obvious reason why they will feel leaner is the prospect of higher interest rates. The longer the boom continues the greater the need for policy to lean against it.

But there is not going to be any fiscal tightening until after the next election. So the curbs will have to come from the Bank of England. That was the unspoken message in the Chancellor's speech: expect higher interest rates.

The only question is by how much they will rise. They would have risen whatever the Chancellor had done, but had he nudged taxes up or trimmed excess fat from public spending the rise would have been more limited. As it is, expect the Bank of England to increase rates to 5 per cent by the end of the year, maybe more next year. It would be loath to provoke a housing crash, so that puts a cap on the rises, but the interest rate cycle has a way to go.

We are drawing towards the end of a period of unprecedented growth - unprecedented for the past 200 years, as Mr Brown reminded us. We will be starting a different period, not one of austerity, not one of catastrophe, but rather one where a greater share of growth will have to be set aside for the future. Things have cooled a bit already, haven't they? They will become cooler yet.