The interbank lending rate at the heart of the banking scandal was until recently relatively unknown outside the City.
Here are some facts about Libor and its history:
The London Interbank Offered Rate (Libor) is a benchmark which governs the rates at which banks are prepared to lend to each other in the wholesale money markets.
Banks use Libor as a basis of swap rates - the borrowing rate between financial institutions. These swap rates are in turn used to determine pricing for a vast range of products around the world, including corporate loans and fixed-deal mortgages.
Banks globally manipulated Libor in the depths of the financial crisis, when interbank rates were soaring, because a high rate reflected badly on the state of a bank's balance sheet.
It spiked to a historic high of 6.8% at the height of the credit crunch, but should be roughly the same as the Bank of England base rate.
In June 2012, Barclays was fined £290 million by US and UK authorities for attempting to manipulate Libor in an effort to paint a flattering picture of its financial health to markets.
Around 20 institutions worldwide have been investigated for possible Libor manipulation following Barclays' settlement.
In August, Royal Bank of Scotland, Barclays and HSBC were among seven banks handed legal notices demanding that they assist in an inquiry by the attorneys general of New York and Connecticut.
UK authorities have come under fire for the part they played in the Libor scandal. It emerged that US Treasury Secretary Timothy Geithner made a series of recommendations for reforming Libor to the Bank of England four years ago, when he was president of the Federal Reserve Bank of New York.