The EU’s single market is called the jewel in the bloc’s crown. Together with the single currency and the Schengen passport-free travel area, it represents one of history’s most consequential voluntary efforts to share sovereignty.

Yet things are not well. As a Financial Times series lays bare, the integration of national markets remains elusive in services, is incomplete in goods, and is in many ways going backwards rather than progressing. Simply put, national authorities leave too many obstacles in the way of equal access to their markets for other member states’ companies and workers: in the history of the single market, only one French baker has ever had their certificate from their home country recognised in Germany. National rules, even if well-intentioned, means cross-border activity must carry the cost of multiple sets of regulations, such as on labelling.

IMF and European Central Bank estimates of these non-tariff barriers are shocking, equivalent to tariffs of 45-65 per cent for goods and 100-110 per cent for services. That is certainly a big overestimate — but as ECB president Christine Lagarde told the FT’s Global Boardroom last week, even if it is only half as much, the cost is still enormous.