It's emerged the Bank of England's Governor discussed the interest rate rigging scandal with a key US official at least four years ago.

A 2008 email trail released by the Bank - between Sir Mervyn King and the then-New York Federal Reserve president Timothy Geithner - raises concerns about Libor fixing.

Estimates out today suggest the issue could cost the world's big banks as much as 14-billion pounds through regulatory fines and damages to investors.