David Andolfatto, head of research at the Federal Reserve Bank of St Louis, has created a minor stir by describing Bitcoin, the virtual currency that has many monetary authorities fretting, as a "stroke of genius", adding it would be "close to impossible" to ban.

Speaking at a local event in Missouri last week, Andolfatto questioned recent efforts to restrict the use of the ‘crypto-currency', asking: "How does one slay the Hydra?"

A raft of central banks have moved to restrict the use of