Some regulatory changes really are earth-shaking. London’s 1986 Big Bang reforms and the US repeal of the Glass-Steagall barriers in banking and insurance upended global finance, opening the way to new competition and consolidation.

Mifid, the European Union’s Market in Financial Instruments Directive, which kicks in on November 1, is not in the same league. Regulators and compliance officers, who have spent the past five years preparing, talk it up, saying it promotes liquidity and investor protection by imposing the same rules across the EU.