What happened in the markets this week? That depends on how often you were looking. It was a brutal Monday — the S&P 500 was down more than 4 per cent, the worst day on the market for more than six years.

Tuesday continued the rout — at least at first. But anyone who had paused for a leisurely coffee on the way to the office might have wondered what all the fuss was about: by 9.25am on Tuesday morning, New York time, the S&P 500 was up 2 per cent from the opening plunge. After various adventures, Tuesday ended up the best day in more than a year.

Twenty-five minutes for coffee is a very long time in the life of a high-frequency trading algorithm, with trades timestamped with an accuracy of one-ten-thousandth of a second. A casual investor, though, can blink and miss it.