I want to talk about currency risk because I think it causes a lot of unnecessary worry for some investors.

But, first, a confession: I am absolutely hopeless at predicting whether one currency will go up or go down relative to another.

And, you know what, I'm not alone. In fact, no one is really much good at it. Certainly, I've learnt that the so-called experts rarely get it right.

Guessing which way one unit of money will move relative to another is, at worst, a mug's game, at best, a lottery.

And I'm not interested in lotteries.