The boss of JP Morgan has said that any Brexit-related job moves will focus simply on serving clients.
Jamie Dimon, whose bank heavily backed the campaign for Britain to Remain in the EU, said London's world-renowned cluster of financial and professional services firms could be fractured by Brexit.
Many across the City are considering what moves they need to make to ensure they can continue serving clients as usual once the UK is no longer a member of the EU.
Speaking to Bloomberg, the JP Morgan chief exec said any moves his firm made would be focused on clients, remarking: "On day one, whenever the exit takes place, JP Morgan has to be able to conduct business with our clients in Europe. That's a sine a qua non."
He continued: "What no one wants is to disrupt financial markets on day one so you can't serve financial companies. That could be devastating."
Dimon also repeated his previous statements that Brexit could cause the bank to move "zero to three, four thousand" jobs away from the UK, but added: "We're just guessing still at this point."
Dimon went on to say he often chinwagged with other banking bosses about how they were handling Brexit, which was one of the benefits of having so many sector big players bunched together in one major city.
"The clustering of financials in London is hugely efficient for all of Europe," he said. "Now you're going to have a declustering which creates huge duplicate costs which is expensive to clients, but we have no choice.
"That's what we've got to do and we're going to find the best way to do it for the client, both for the long-run and the short-run."
Dimon's words have echoes of comments made last October by Jon Cunliffe, deputy governor with responsibility for financial stability at the Bank of England, who said other major European cities would be unable to mimic London's financial ecosystem for quite some time.