SEBI has banned the firm from India’s securities markets. The drama has thrown a bright light on Jane Street, a company of legendary opacity even in an industry that prioritises secrecy. And it could carry political and regulatory consequences, not just for Jane Street, but for an entire, ascendant industry of marketmakers.

Whether arbitrage or manipulation, the Jane Street episode highlights a critical truth: markets need more transparency, more accountability, and more human judgment.

Jane Street has told staff it will contest a ban by India's financial regulator which has accused the U.S. high-frequency trading giant of market manipulation, adding that its practices in question were "basic index arbitrage trading".