The humble anchovy is set to become the focus of the first court trade war between Britain and the European Union since Brexit.

Britain has banned European ships from fishing for the silvery fish in its North Sea waters to protect marine wildlife that depends on it for food.

But the EU challenged the move, saying it violated a post-Brexit trade deal by discriminating against Danish vessels commercially fishing for sandalfish.

The dispute is now heading to a three-day trade tribunal hearing after formal talks to resolve it failed.

If no last-minute compromise is reached, it would mark the first time the parties have gone to arbitration under Boris Johnson's 2021 trade deal.

The case will be heard next Tuesday by a panel of three mutually agreed international trade judges at the Permanent Court of Arbitration, the dispute resolution body in The Hague.

They could defend the UK's position or order the UK to change or abandon the ban, in which case Brussels could eventually retaliate with tariffs on UK exports if ministers refuse to comply.

Under the trade deal, a final ruling must be made by the end of April, although it could be issued earlier. No right of appeal.

Meanwhile, Britain is preparing for thorny negotiations with the European Union over new fishing restrictions from next June, when existing arrangements under the trade deal expire.

Sir Keir Starmer also hopes to persuade EU leaders to agree new deals in areas such as security and food trade as part of a wider "reset" in relations with the UK.

Loach, a group of small eel-like fish, is a fish population that is jointly managed under the trade agreement. It is not captured for culinary reasons and is unlikely to be found on restaurant menus in European capitals.

But it is a favorite food of other fish such as cod and haddock, as well as threatened seabirds such as puffins and kittiwakes.

The UK has effectively blocked its own vessels from fishing for the species through its licensing system since 2021, citing the need to prevent overfishing and protect the North Sea ecosystem.

Last March, Rishi Sunak's Conservative government banned all vessels from fishing the species in British waters, and ministers in the SNP-led Scottish government imposed a similar ban in Scottish waters.

It won plaudits from UK dialogue groups, which have long campaigned for an outright ban, which Sir Keir's Labor government has retained since coming to power in July.

But this has angered Danish fishermen, who sell sandal eels to animal feed and fish oil producers, and who are entitled to catch the vast majority of the EU species in British waters under a post-Brexit trade deal.

The dispute centers on whether the UK's restrictions on the rights of trawlers for conservation reasons unnecessarily limit EU-agreed fishing rights.

In its submission to the court, the EU argued that scientific modeling of stock levels or the "economic and social impact" on Danish fishing communities did not justify the geographic scope of the ban.

The UK government's detailed response has not yet been released, but a spokesperson told the BBC that the UK government is committed to protecting the environment in line with its trade commitments.

Its decision to continue the ban was backed by an unlikely alliance of three political parties, environmental groups and staunch Brexiteers.

The renewable energy industry has also taken an interest, arguing that the ban would help seabirds achieve the necessary level of "resilience" to allow more wind farms to be built while still meeting conservation targets.

The UK has previously estimated that the anchovies caught in its waters are worth around £45m a year, making the industry small in the context of wider trading relations.

But the dispute will be closely watched to see how judges balance Britain's right to take protective measures against economic rights.