Please be aware that this margin is marked-to-market in real time for the life of the trade, which is standard market protocol. Therefore, if the GBP/USD mid-price increased theoretically to 2.0700, the margin required to maintain the trade would be GBP 1,000 x 2.0700 or $2,070. If the price fell to 1.9500 then the required margin would decrease accordingly.