In the run-up to last year’s referendum, some grave-faced pundits predicted that Brexit would prompt a mass exodus of bankers from London to Frankfurt. Nonsense, said the Leavers. Everything will be fine. As with almost every aspect of the campaign, there was virtually no common ground. Depending on which side you listened to, either the Square Mile would become a wasteland or Brexit would make no difference whatsoever. So, fifteen months later, who should we believe? I’ve been talking to German bankers and it’s no surprise to find that the word on Threadneedle Street is a lot more nuanced. Project Fear wasn’t entirely fanciful, they tell me, but the timescale was all wrong.

There will be a drift from London to the Continent, my sources say, but it’ll be a gradual process – taking years (or even decades) to play out. Relocating an entire office to another country is an extremely expensive business, and banks want to make absolutely sure they’re making the right move. No point moving, then finding that Britain has struck a Brexit deal which makes a move unnecessary. Even worse to move, then find you’ve picked the wrong place. The problem for German bankers based in London is, they don’t know what sort of Brexit deal Britain is trying to strike (let alone whether they’ll get it) and they suspect the British Government doesn’t really know either. German bankers don’t want a hard Brexit or a soft Brexit – they just want some clarity from the British Government. Hence they’re biding their time, and waiting for the process to play out. They suspect they may have a long wait.

We’ve all heard a lot about ‘passporting’ lately – whereby banks in EU member states can trade securities for clients right across the European Union without having to obtain prior clearance from regulators in every other EU country. Unless David Davis can strike an amazing deal with Michel Barnier, it looks like Britain will lose these rights, making London far less attractive for any bank which does substantial trade with the EU. Passporting isn’t essential for every aspect of a bank’s business but, like most institutions, banks prefer to have everything in the same place. It’s frustrating and expensive to split your operations between several sites in several countries. There’s still a lot a London-based bank can do without EU passport rights, but in the long run you want as much as possible under one roof.

Of course, London’s assets as a banking centre aren’t confined to its EU membership. If it was, these German bankers never would have left Frankfurt in the first place. London is bigger, more cosmopolitan and better connected than Frankfurt. It’s Anglophone (a huge advantage) and far more appealing to millennials – a big plus when you’re trying to headhunt the best young talent from across the globe. These assets won’t vanish overnight (even after a hard Brexit) but eventually they’ll be outweighed by the disadvantages of being outside the EU, and when that time comes it'll be time to leave.

So when that happens, where to go? German bankers are currently weighing up several options. Firstly, forget about remote working. Face time is still crucial. Banks want to be around other banks – that’s one of the things that makes London so appealing (for the time being). Wherever German banks go next, they’ll want to gather in the same place. Frankfurt already has the infrastructure, but Berlin is far more sexy – a significant factor when you’re trying to persuade rising stars to leave London. Paris is another candidate but the dark horse is Dublin. When Britain leaves in 2019, the Irish capital will become the biggest English speaking city in the EU. Brexit has been a big headache for the new Irish Taoiseach, Leo Varadkar, but if German bankers decide to cross the Irish Sea rather than returning to the Continent, it could prove to be a massive boost for Dublin, and the Irish Republic as a whole.