It’s no secret that Britain’s negotiations with the European Union over the terms of its departure are going to be unfathomably complex.

Some opposed to Brexit fear that the two-year window that the UK will have to negotiate these terms after Article 50 is triggered just won’t be long enough — and it sounds like the British government might be preparing for that eventuality as well.

According to a new report from Politico, the UK is secretly investigating the possibility of a “Plan B” with the EU: A ten-year interim deal while everything else is hashed out.

Such an agreement could keep trade tariffs between the EU and the UK at zero for a decade — providing some measure of stability while the rest of Britain’s Brexit terms are hashed out. Otherwise, the UK could see itself hit by automatic tariffs on a range of goods as it falls back on World Trade Organisation (WTO) rules as a no-deal default.

Clearly, the protracted uncertainty an interim deal would cause would not be advisable — and the UK government will aim to secure a comprehensive deal within a two-year timeframe. But the report suggests that the UK is quietly taking seriously the possibility that one will not be achieved.

Prime Minister Theresa May — and other British politicians — has previously said that no deal would be better for Britain than leaving the EU with a bad deal. But such a “Plan B” would suggest they’re keen to avoid the “no deal” option if at all possible, even if it means years more of negotiations.

Politico reports that this kind of interim deal would be possible because a WTO clause allows a “reasonable amount of time” to agree upon a deal before automatic tariffs came into play.

May has said she intends to trigger Article 50 by the end of March, meaning Britain’s exit should theoretically be finalised by March 2019.

But if this “Plan B” is ultimately used, the Brexit debate may not be over until many years after that.

More from Business Insider UK:

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.