QE may well help a bit, and it was the right thing to do, mainly because there wasn’t much else available. But it is not a game-changer. For a start, the amount announced – one trillion euros – sounds huge, but in fact all that purchases of this amount would do is to restore the size of the ECB’s balance sheet to where it was in 2012.

This would mean that since the beginning of the financial crisis of 2008 it would have grown by about 150pc, compared with about 400pc for the US Fed and about 300pc for the Bank of England.

Moreover, most of the ways that QE is supposed to operate would not work very well in current conditions. The policy will make the banks flush with cash – but they have been flush with cash anyway. Forcing down bond yields should reduce the cost of finance and boost asset prices, but yields were already at rock bottom and in any case, in Europe, most borrowing is done from banks, not from the markets.

The main channel through which QE is going to influence the economy is the exchange rate. The lower euro – and it has already fallen by almost 10pc since August – will raise import prices directly and hence help to fend off deflation – at least for a while – and it should help to boost exports and reduce imports, thereby tending to raise real GDP. But it is unlikely that this effect will be big. The eurozone exports about 20pc of its GDP. By contrast, the UK exports roughly 30pc.In so far as the exchange rate is the main tool of macroeconomic adjustment for the eurozone, this is deeply ironic, because it is, of course, precisely this tool that the members of the eurozone have given up between themselves. If the euro did not exist, then the market would long ago have sent the currencies of the weaker southern bloc sharply lower and the currencies of the northern bloc sharply higher.

David Fuller's view

It is hard to see a successful resolution to the Northern versus Southern European divide, which is why I think the Euro will eventually break into at least two different shared currencies.  Meanwhile, Mario Draghi has probably bought at least two years of reasonable stability with his QE programme.