A staggered introduction of the EU's revised trading rulebook would have been helpful for financial firms trying to get to grips with the radical changes, according to the head of the regulator that will implement them in the UK.

Speaking at a Bloomberg conference on February 4 on the revised Markets in Financial Instruments Directive, Tracey McDermott, acting chief executive of the Financial Conduct Authority, said it "would have been helpful if the framework legislation [for Mifid II] had allowed for the phasing in of the transparency regime".