The dispute centres on whether the UK’s right to restrict trawlers for conservation reasons unnecessarily restricts agreed EU fishing rights.

In its submissions to the court, the EU has argued the geographical scope of the ban is not justified by the scientific modelling on stock levels, or the “economic and social impacts” on Danish fishing communities.

In a response published by the court, the UK has defended the scientific advice behind the ban, adding that the EU has failed to point out “any superior model” available at the time.

It added that the UK was within its rights to bring in the ban, highlighting that the trade agreement itself commits both sides to taking account of the impact of fishing on marine diversity.

The UK decision to continue the ban has been backed by an unlikely coalition stretching across three political parties, conservation groups and committed Brexiteers.

The renewable energy industry has also taken an interest, arguing the ban helps achieve the necessary level of seabird “resilience” to allow more wind farms to be built whilst still hitting conservation targets.

The UK has previously estimated sandeel caught in its waters is worth around £45m a year, a tiny industry in the context of the wider trade relationship.

But the dispute will be watched closely for how the judges balance the UK’s right to take conservation measures with economic rights.