The future EU-UK relationship cannot be negotiated in abstracto as a purist form of ‘taking back control’, as imagined by Prime Minister Boris Johnson. The UK is the first country to leave the EU, but the last of a long list of close neighbours and remote countries which have asked for preferential access to the Union’s Single Market. Any post-Brexit agreement will have to fit into an already complex framework of external differentiated integration. Over the years, the EU has accepted very diverse modes of such integration. Every agreement corresponds to a specific moment of the EU project, a specific partner and specific objectives, and is implemented through a specific institutional set-up.
However, while the UK expects to benefit from this ad hoc approach to obtain a tailormade post-Brexit agreement, a rather systemic approach is prevailing with EU negotiators. The latter must carefully anticipate any spillover effects of a final deal on the Single Market; on member states as much as on countries benefiting from specific forms of external differentiated integration.

The global economic crisis provoked by the COVID-19 pandemic has deeply transformed the post-Brexit political economy. Avoiding the additional economic costs of a hard Brexit could be an incentive for concession. However, now more than ever, the EU27’s priority, reflected in its negotiating mandate for post-Brexit relations, is to safeguard its economic competitiveness by preserving the integrity of the Single Market and using the full leverage of its economic weight on third countries.

While (i) the EU had launched a review of the various existing differentiated integration agreements even before the 2016 referendum, (ii) Brexit has been an additional incentive to increase EU control over preferential partners. Brexit led to a harder EU stance on unified framework agreements with stronger institutional mechanisms to ensure a level playing field with third countries. From this, it follows that (iii) rather than facilitate differentiation in integration, Brexit might even be a turning point to upgrade the Single Market’s leverage. ▪▪▪