Central banks might one day issue their own digital currencies, according to Chris Salmon, the Bank of England's chief cashier, speaking last night at a panel discussion on Bitcoin.

At the event held at London's Chatham House, Salmon said it is "exceedingly unlikely" central banks will issue digital money in the next decade but conceded "it is possible over a longer horizon".

Alternative currencies – defined by Salmon as "a means of payment that sits outside of the formal banking system" –