India has been a money machine for Jane Street, netting the trading giant more than $4bn in profits in just over two years. But it is now the source of a scandal that is imperilling the Wall Street firm’s golden run.

Jane Street has been barred from the Indian securities market by its markets regulator, which has said the U.S. firm used its trading strategies to "manipulate" a key stock market index, leading to losses for millions of retail investors,