The G20 duly came up with a standard, anodyne concoction of a statement extolling the virtues of "motherhood and apple pie" in the strongest possible terms, with the unspoken threat that currency war criminals would be subject to the full force of international law, including if necessary, in extreme cases, a couple of hours on the "naughty step".

Perhaps not surprisingly, the market's conclusion is that Prime Minister Shinzo Abe may not be unduly concerned about this possible punishment and so he will carry on with his all too overdue efforts to revitalise the Japanese economy, and probably with unaccustomed vigour compared with 20 years' worth of predecessors.

So is that it, 100 here we come in USDJPY, say? Well, yes, that's in all probability where we're going, but having spent 31 years in these markets I don’t expect the pair to move in a completely straight line. First of all, there's the little matter of the "front page of the business news" test. I find this a fantastically useful saw - by the time a story is on these pages, every trader, his or her granny and her cat have got the position on and there's bound to be at least a small hiatus in the move. The yen short certainly qualifies.

I'd also suggest caution ahead of next weekend's Italian election. I'd say there's a one-in-three chance of a market-unfriendly outcome, which puts the continuing pace of fiscal and employment reform in some jeopardy - probably involving a fair amount of racing to safe havens, if they come to pass and very possibly even before the weekend, driven by fear of those outcomes.

The yen would still benefit in that case and, given market positioning, it could get ugly. Remember, USDJPY goes up by the stairs and down by the elevator shaft. Anyone else remember October 1998? I'd sell the yen next week - always leave some crumbs on the table!