Nathan Rotschild had a webb of spy
According to the result of the battle, the Englissh pound would drop or rise
He received early rapport, and begin to sell big amount of £ in London, creating a panic, lot of peoples begin to sell and the £ value dropped rapidly . Then he bought at low level before any official news came in about the battle
When the success of the battle was known, the £ rised and rised, giving him a large profit
Best