The foreign exchange market is not easy to manipulate.
But it is still possible for traders to change the value of a currency in order to make a profit.
As it is a 24-hour market, it is not easy to see how much the market is worth on a given day.
Institutions find it useful to take a snapshot of how much is being bought and sold. Until February, this happened every day in the 30 seconds before and after 16:00 in London and the result is known as the 4pm fix, or just the fix.
Since these violations came to light, the window has been changed to five minutes to make it harder to manipulate.
The fix is very important, as it is the peg on which many other financial markets depend.
So how do you make currency prices change in the way you want?
Traders can affect market prices by submitting a rush of orders during the window when the fix is set.
This can skew the market's impression of supply and demand, so changing the price.
