Cryptocurrencies, which first emerged in the wake of the global financial crisis, offered a vision of money free from central bank control. Since their creation, they have boomed into a highly volatile and divisive asset class.
Bitcoin, the most traded cryptocurrency by volume, has a market value of around $700bn alone, according to CoinMarketCap, but can suffer huge losses from a single tweet.
Policymakers have grown increasingly concerned about potential fallout from cryptocurrency markets, launching crackdowns and regulatory consultations. Proponents argue cryptocurrencies offer an alternative to centralised financial systems, a way to wrest control from central banks and stimulate innovation; but the market has also been exploited by fraudsters, while their creation has raised environmental concerns and the spectre of wider financial implications.