The price of bitcoin has smashed through $5,000 to an all-time high: the cryptocurrency rose by more than 8% to $5,240, having started the year at $966. Bitcoin has soared by more than 750% in the past year and is worth four times as much as an ounce of gold. The soaring value of bitcoin and other cryptocurrencies comes despite growing warnings over a price bubble. The starkest warning came from the JP Morgan chief executive, Jamie Dimon, who said bitcoin was a fraud that will ultimately blow up. Speaking last month, he said there was a limited market for the digital currency, arguing that it was only fit for use by drug dealers, murderers, and people living in countries such as North Korea.