Markets took a deep breath on Tuesday after Wall Street’s shock start to the week, with the emergence of cheap Chinese artificial intelligence rival DeepSeek lopping more than half a trillion dollars off what had been America’s most valuable firm Nvidia. Nvidia’s 17% one-day drop marked the biggest loss in market capitalisation for a single stock ever, outstripping its own record from last September. Vistra dropped 28.3% and Constellation Energy fell 20%.