The UK has announced that it will ratify the Unified Patent Court Agreement, a key step needed to bring the unitary patent and Unified Patent Court (UPC) into being.

But it has taken many by surprise as it was expected that the vote to leave the EU meant that Britain wouldn't be able to accept the supremacy of Europe's top court, the Court of Justice of the European Union (CJEU), something the Unified Patent Court Agreement (UPCA) requires.

But Article 20 of the UPCA states: "The [unified patent] Court shall apply [European] Union law in its entirety and shall respect its primacy," while Article 21 insists: "Decisions of the Court of Justice of the European Union shall be binding on the court."

Once it has ratified the UPCA, the UK will be obliged to follow the decisions of the CJEU insofar as they concern the unitary patent.

The UK government is acutely aware that this is problematic. Whitehall's statement on the move to ratify emphasises: "the decision to proceed with ratification should not be seen as pre-empting the UK’s objectives or position in the forthcoming negotiations with the EU." And adds: "The UPC itself is not an EU institution, it is an international patent court. The judiciary appointed include UK judges."

The European Patent Office (EPO), which will be overseeing the new system, welcomed the news. In a statement sent to Ars, EPO president Benoît Battistelli said: "This important news from the UK government means that the long-awaited court is soon to be realised."

The unitary patent system can only come into effect when at least 13 EPO member states have ratified the UPCA, including France, Germany, and the UK. So far, 11 have done so, among them France, and ratification is advanced in Germany. Following the UK's announcement that it too will proceed with ratification, Battistelli explained: "The way is now clear for the last few ratifications to take place in the coming months, and the new court to start work soon after."

One important benefit of the new system for the UK is that alongside the central seat in Paris, the UPC will have a specialist section in London, which will hear cases relating to chemistry, including pharmaceuticals and the life sciences. An office has already been found for the London division in Aldgate Tower.

However, the existence of a section in London will make withdrawing from the unitary patent system even messier. Pulling out again so soon after ratifying the agreement is still a real possibility if a so-called "Hard Brexit" takes place, and it's something that UK tech companies are already fretting about.

As Antony Walker, deputy CEO of the techUK association of companies, said in a statement: "Now it has been confirmed that the UK will take part in the Unitary Patent it is in the interest of UK tech that it will not be removed from the new system at some point in the future."

With Brexit looming, that's going to be difficult to achieve.

In her Tory conference speech, prime minister Theresa May promised: "Our laws will be made not in Brussels but in Westminster. The judges interpreting those laws will sit not in Luxembourg but in courts in this country. The authority of EU law in Britain will end."

If the Brexit notes reportedly held by an advisor in Downing Street on Monday are anything to go by, that is still likely to be the overall aim.

But if the UK wishes to remain in the UPC system, an exception will have to be made for patents, with judges sitting in Luxembourg still interpreting the law that applies in the UK. Some Brexiters may therefore see the government's announcement as a sign that Brexit no longer means Brexit.