(Daily Mail) — A mystery investor or hedge fund reportedly made a bet of almost $1billion at odds of 10/1 last month that the U.S. would lose its AAA credit rating.

Now questions are being asked of whether the trader had inside information before placing the $850million bet in the futures market.

There are mounting rumours that investor George Soros, 80, famously known as ‘the man who broke the Bank of England’, could be involved.

He made more than $1billion on currency speculation when the British pound left the Exchange Rate Mechanism on Black Wednesday in 1992.

The latest bet was made on July 21 on trades of 5,370 ten-year Treasury futures and 3,100 Treasury bond futures, reported ETF Daily News.

Now the investor’s gamble seems to have paid off after Standard and Poor’s issued a credit rating downgrade from AAA to AA+ last Friday.

Whoever it is stands to earn a 1,000 per cent return on their money, with the expectation that interest rates will be going up after the downgrade.