BREXIT is a mess. Every day there seems to be a new plan that gets struck down by backbenchers or EU negotiators or another minister who’s fallen on their sword.

Many people have given up following the twists, turns, tragedies and glimmers of hope. They already have television soap operas; they don’t need another tortuous drama.

But Brexit is probably the most important factor affecting UK financial markets right now and it has huge implications for everything from your mortgage and pension through to any investments you’ve made. Our job is taking care of people’s investments, but unfortunately we can’t simply change the channel on Brexit.

It can be demoralising trying to figure out what’s happening with Brexit, as we simply don’t have the answers to so many questions. Even after careful analysis, the honest answer to most questions about secession is: “We don’t know.”

We’re not sure anybody – including the politicians – does. But it turns out there’s actually quite a lot of information to be gleaned in “we don’t know”, if we organise our thoughts logically.

We created a simple decision tree to help us filter out the day-to-day noise and make sense of how Brexit could develop over the coming year. It starts with the overarching question, can the Government strike a plausible deal with the EU? We believe there is a strong probability that it can – there’s just too much at stake on both sides of the Channel for it not to.

As for whether it can do it in a timely manner, we think the chances are a coin toss (mathematics for “don’t know”).

And if the Government does arrange a deal before 29 March 2019, would it pass politicians? That’s another “don’t know”, but if it did we think it would be with the cross-party agreement of everybody bar the Tory hardliners led by Jacob Rees-Mogg.

We consider that that would be a sandstone Brexit, named after the softest rock – and so representing the softest hard Brexit - you can find. If the Government and the EU cannot come to terms at all, there are two choices as we see it: a straight hard Brexit or a second referendum. We think the chance of one or the other happening is 50-50.

When we calculate the probabilities we find that by far the most likely result is a never-ending story. The politicians agree on principles but not the details. In short, they keep kicking the can down the road.

In such a scenario, sterling would likely amble lower, benefiting investors who are light on small and mid-cap UK assets and instead hold foreign investments and the FTSE 100, which tend to do well when the pound weakens.

A hard Brexit has the second-highest probability. A no-deal break with the EU would send sterling tumbling as low as $1.20 or more, we believe. Again, holders of overseas assets and the FTSE 100 would probably do best.

Then comes our sandstone option, followed by a no Brexit. According to our decision tree, the only way Brexit will be abandoned is if Remain wins a second referendum. Both sandstone and no Brexit would boost sterling, we believe, as they would dispel the uncertainties that are delaying investment – and potential GDP growth – in the UK. They would boost small and mid-sized UK companies, while a stronger sterling would hurt the FTSE 100 and overseas investments.

Given a never-ending story or hard Brexit appears most likely, we prefer to hold the FTSE 100, which would benefit from weaker sterling. If any kind of Brexit deal is struck, there’s a good chance that many foreign investors will return to UK assets – including the FTSE 100 – pushing up stock prices. That relief-buying of the FTSE 100 could even offset the usual falls that come with sterling strength.

That’s why we are still happy to hold some UK investments, despite the current confusion caused by Brexit.

David Coombs is head of multi-asset investments at Rathbones.