AFTER years of rule-drafting, industry lobbying and plenty of last-minute wrangling, Europe’s massive new financial regulation, MiFID 2, was rolled out on January 3rd. Firms had spent months dreading (in some cases) or eagerly awaiting (in others) the “day of the MiFID” when the law’s new reporting requirements would enter into force. One electronic-trading platform, Tradeweb, even gave its clients a “MiFID clock” to count down to it.

Apprehension was understandable. The new EU law, the second iteration of the Markets in Financial Instruments Directive (its full, unwieldy name), affects markets in everything from shares to bonds to derivatives. It seeks to open up opaque markets by forcing brokers and trading venues to report prices publicly, in close to real time for those assets deemed liquid. It also requires them to report to regulators up to 65 separate data points on every trade, with the aim of avoiding market abuse.

The changes are greatest for markets, like those in bonds and derivatives, that are now largely conducted “over the counter” (ie, not on exchanges). But the law also restricts share trading in “dark pools” closed to retail investors, provides for access to European markets for non-EU firms, and requires investment banks to start charging separately for research, among myriad other provisions. It is perhaps the biggest regulatory change to European financial markets since the financial crisis.

For all the jitters, the first hours of trading under the new regime went fairly smoothly, though trading volumes were lower than usual. Financial firms had collectively spent $2.1bn preparing for MiFID 2 in 2017 alone, according to one estimate by Expand, part of the Boston Consulting Group, and IHS Markit, a data provider.

Some banks had people up all the night before the 3rd. The preparations paid off. But regulatory reprieves also helped. In late December the European Securities and Markets Authority (ESMA), an EU regulator, granted a six-month reprieve from the requirement that every counterparty to a trade must have a “legal-entity identifier”, a unique number, after many firms failed to obtain these in time. It also let trading continue across the EU even though 17 of its members had not yet fully transposed the rules into national law. And ESMA clarified that trading on non-EU venues could continue while it finishes its assessment of which jurisdictions will be deemed “equivalent”. This avoided a worst-case scenario, in which European traders suddenly lost access to the New York Stock Exchange, say, or the Chicago Mercantile Exchange.

Early on January 3rd itself, Germany’s and Britain’s regulators allowed three large futures exchanges—Eurex Clearing in Frankfurt, and ICE Futures Europe and the London Metal Exchange in Britain—to delay implementation of “open access” provisions until mid-2020. These rules, divorcing the execution of futures contracts from the clearing of them (they now occur at the same exchange), were contentious when passed, with Britain reportedly a strong proponent and Germany staunchly opposed. A London lawyer thinks the long delay, to past the date in 2019 when Britain is to leave the EU, may well mean these provisions “never see the light of day”.

Significant as they may be for parts of the market, such reprieves do not amount to a delay of the overall law, says Jonathan Herbst of Norton Rose Fulbright, a law firm. Nonetheless, a disaster-free implementation day does not mean the end of the worries. As Enrico Bruni of Tradeweb points out, market participants will adjust their trading patterns over time, and emerging problems will need to be resolved. It will take even longer to see if the structural changes the new framework is forecast to encourage—such as consolidation among brokers or asset managers—materialise. And the law may yet play a role in the Brexit negotiations. Its rules on financial-market access for third countries, after all, will apply to Britain. There are many more days of the MiFID to come.