For most of the week the euro was playing a waiting game, waiting for the European Central Bank to make its big announcement on Thursday. Having been primed by president Mario Draghi more than a month ago, investors were expecting another dose of "whatever it takes" to get euro zone inflation back up to its 2% target. That expectation was fed by Wednesday's provisional consumer price index data, which put inflation at just 0.1%.

In the event, the ECB said it would cut its deposit rate from -0.2% to -0.3% and extend its asset purchase programme for another six months. To say the least, the news came as an anticlimax. The euro shot higher, strengthening by 2% against sterling. On the week it is up by four cents - 3% - against the pound and by a roughly similar proportion against the US dollar.