In the autumn of 1998, I bumped into a senior official at Long Term Capital Management, the US hedge fund, in a carpark in Tokyo (where I then worked). I’ve never forgotten the sight: not only was he haggard but his hair had turned almost white, seemingly overnight.

No wonder. As I later discovered, that was the day LTCM was on the verge of implosion. And one factor driving that meltdown was a storm in Tokyo’s currency markets. Global hedge funds frantically unwound carry trades they had made using the yen – propelling the Japanese currency 18 per cent higher in three turbulent days.