During BBC’s Today program on Tuesday, Sir Jon Cunliffe, Bank of England’s deputy governor, warned investors about the risks of cryptos becoming worthless assets.

After acknowledging that cryptos have been growing very fast and becoming mainstream, Cunliffe mentioned that they could pose a risk to the whole financial system, even if only 0.1% of U.K. households’ wealth is now held in cryptos. He mentioned that the prices of cryptos, including bitcoin, could drop to zero.