When is currency intervention not currency intervention? When it is practised by the European Central Bank, apparently.

You've got to hand it to Wim Duisenberg and his colleagues. For a crew that has singularly failed to show any subtlety in its handling of the new currency, it pulled some stunt in the hours ahead of its decision not to raise rates further this week.

Fearful no doubt about currency speculators preying on the euro following such a "no change" announcement, it decided to use the interest it has earned on its foreign currency reserves to buy euros.

Technically speaking, it may not be intervention but, as the old saying goes: if it looks like a duck, walks like a duck and sounds like a duck, the chances are it is a duck.

Moreover, it is the first time the ECB has taken any action to underpin the currency, as against trying to talk it up.

Might it be that Mr Duisenberg is testing the waters to see what the reaction to any concerted intervention might be?