Eight seconds may not sound like a long time. But in the modern financial world, it’s a valuable head start that can give traders a crucial edge.

That’s why the Bank of England will be mortified that some traders have been listening to its press conferences before the rest of the City was able to.

Those press conferences regularly move currencies, shares and bonds, as journalists question the Bank’s governor, Mark Carney, about the state of the economy and the prospect of interest rate changes.

Sterling traders learned this lesson during an inflation report press conference in February, in which the governor discussed the bank’s assessment of the UK economy. The pound slumped to a two-week low of $1.2854 when the Bank issued its worst growth forecasts in a decade. But it then quickly rallied, spiking to $1.2997 after Carney said a reduction in Brexit uncertainty would help the economy.

Traders who had shorted the pound, having seen the grim forecasts, would have suffered losses as it strengthened. But a speculator with their ear pressed to the Bank’s hacked audio feed could swiftly sell dollars and buy pounds when they heard Carney sounding optimistic, then do the opposite at a profit once the rest of the market caught up.

Time it right, and you’d make more than 1% before the press conference was over, or perhaps $11,000 (£8,500) for every $1m moved into sterling.

Thanks to algorithmic trading, even a second’s head start would be ample time to profit and catch rivals on the hop. For high-frequency traders, every millisecond counts.

A decade ago, a company called Spread Networks built an 827-mile (1,330km) high-speed fibre line between Chicago and New Jersey to shave four milliseconds off the trading time to 13 milliseconds. Hedge funds paid $10.6m each to use the line, and profit from discrepancies between stock prices in New York and futures in Chicago.

Those speculators used high-frequency trading strategies – placing large volumes of trades across different markets, often trying to profit from marginal movements in share or currency markets.

Brexit uncertainty means any head start would be especially valuable. Some foreign exchange traders nicknamed the pound the “Great British peso” when it became even more volatile than the Mexican currency. They also joke about “playing the forex”, a reminder that gains can vanish in the blink of an eye. Eight seconds is ample time for a few blinks, or a rush of buy or sell orders.

But there could be consequences for those who took advantage of the illicit audio feed. Tony Katz, the head of financial services and investigations at DLA Piper, said: “The FCA [Financial Conduct Authority] will, in all likelihood, be investigating those who have sought to take advantage of potential inside information, and will take appropriate action should any evidence be found.”