“NO EUROPE à la carte.” “The four freedoms are indivisible.” “There can be no cherry-picking.” It takes a lot to get the European Union’s leaders to agree, but Britain’s vote to leave has managed it. The merest hint from Brexiteers that they might seek the full benefits of the EU’s single market while curbing immigration was enough to galvanise the rest of the club to action. Angela Merkel, Germany’s chancellor, emphasised the point again this week: Britain could expect no “free access” to the single market if it shut its borders to EU workers.

Ah, the single market. The €14-trillion ($15.6 trillion) jewel in the EU’s crown, the pinnacle of European integration. Unlike the single currency it covers all EU members and is largely considered a success, generating a 2.1% increase in GDP in its first 15 years. it has quickly acquired a totemic role in debates on both sides of the English channel. Almost half of Britain’s exports by value go to the rest of the EU; any curbs on that trade could seriously injure an economy already tumbling towards recession. On the EU side, governments trying to hold their fracturing club together are hardly minded to offer privileged market access to a country that has chosen to leave.

More than a traditional free-trade area, the single market eases intra-EU commerce by reducing non-tariff barriers, facilitating capital flows and trade in services, and granting full mobility to European workers, a right 7m have chosen to exploit. (Hence the “four freedoms”: movement of goods, services, people and capital.) The idea is to allow Europe’s businesses to operate as freely across borders as within them.

If only. Although goods are easily traded and EU citizens have the right to live and work where they please, elsewhere the single market remains a work in progress. Energy, finance and transport markets are far from integrated. The service sector, 70% of the EU economy, is particularly hampered: in 2012 it accounted for only one-fifth of intra-EU trade. Professions are often hard for outsiders to penetrate, thanks to licensing rules, training requirements and other barriers to entry. Ask architects or notaries trying to set up shop outside their home country, or anyone trying to break into Germany’s heavily regulated (and low-growth) services sector. Some countries have over 400 regulated professions. A special diploma is needed to become a corset-maker in Austria.

The European Commission, which polices the single market, has tried to prise open some of the more protected areas of Europe’s economy. A services directive in 2006 cut red tape and made it easier for firms to establish operations abroad, but its scope was limited and implementation patchy. A “single-market strategy”, launched almost unnoticed last October, sought to do better at applying existing rules. But this is hardly visionary stuff.

Among the first to argue that this was hypocritical was John Major, a former British prime minister. In a speech in 2014 warning of the risk of Brexit, he suggested that the incomplete EU market in services was reason not to be dogmatic on labour mobility. If Germany could, in effect, limit foreign businesses from operating inside its borders, why should Britain not cap EU migrants? That argument seemed reasonable in Britain, where high EU immigration rates had become divisive, but found scant support on the continent. Some governments even grumbled at the terminology: EU workers are not “migrants”, they fumed, but citizens with legitimate free-movement rights. They had a point: plenty of services can only be delivered in person (think waiters or tattoo artists). Herein lies the “indivisibility” of the four freedoms.

But the energy devoted to defending the single market is apparently not available for deepening it. Jean-Claude Juncker, the commission’s current boss, took office almost two years ago vowing to accelerate integration in energy, digital services and Europe’s fragmented capital markets. But progress has been slow (and Jonathan Hill, the British commissioner in charge of the capital-markets union project, resigned after the Brexit vote). Consumer-friendly measures, such as preventing “geoblocking” (altering website access for users in different countries), will grab headlines but are unlikely to do much for growth.

The market that Jacques built

That is a shame. Or, as one senior EU official puts it, “it is borderline criminal”. The commission reckons that merely implementing current law on services trade could boost EU output by 1.8%. A proper digital market could add 3%. Other estimates are higher. Across the EU growth is slow, investment low and, in most countries, fiscal space limited. Deepening the single market looks like a good way to boost long-term output. And yet progress has ground almost to a halt. Why?

First, the low-hanging fruit has been plucked. It is much easier to liberalise trade in goods than in jealously protected services markets, as the EU has learned during its painful attempts to negotiate “next-generation” trade deals with Canada and America. Second, the euro crisis forced governments to focus on macroeconomic stability rather than the fiddly business of market regulation. Third, the commission is not the mighty beast that, under the guidance of a French Socialist, Jacques Delors, assembled the rudiments of the single market in the 1980s. Today power in the EU rests firmly with governments, and few seem minded to take on vested interests at home when the benefits of freer trade will be so diffuse. One Brussels-based lobbyist notes ruefully that in 2008 industrial firms tried to stop the commission from regulating so much. Now they are desperate for it to be more aggressive.

Calls to deepen the single market will not go away, but they are starting to acquire a sepia tinge. Momentum has stalled and looks unlikely to pick up, not least because the departure of Britain will deprive the single market of its biggest champion. For some, who never trusted the EU’s great project of liberalisation, that is no great loss. Others may come to regret it.