Bitcoin is the fastest-growing asset in the world this year, but the virtual currency does not appear to have many users in London’s tech district. It has been more than a month since bitcoin was used to buy a flat white or craft beer sold at the Old Shoreditch Station, according to the hospitality manager at the east London bar.  Bitcoin is a digital currency, also known as a cryptocurrency, that emerged after the financial crisis and is not underpinned by a central bank. It allows people to bypass banks and traditional payment methods for goods and services – an idea that has evidently caught the imagination of some investors, because its price has surged by more than 900% in 2017. Bitcoin – created by “miners” who use high-powered computers to solve complex mathematical problems – must be stored online using a digital wallet, and can be bought or sold using exchanges such as Bitstamp, Bithumb and Kraken.