If, when the dust settles, there is no Brexit after all, then any money spent now on setting up for an exit will have been wasted. The way for a commercial outfit to minimize their cost and risk is to implement their exit strategy now, and if it turns out that there is an implementation period, that will be good news.

And if there is no Brexit after all, then the cheapest thing to do will be to retain whatever arrangements were made in preparation for Brexit, which means that no-Brexit is not the same as "going back to how things were before this all started," it is more like "you wanted us out of here, so we are out."

A bank that has just moved thousands of workers and IT systems to Frankfurt is not going to be in a rush to move them back to London next April.