Barclays has been given the green light to transfer €190 billion worth of assets to Ireland.
The banking giant received approval from the High Court in London for the move, which involves 5,000 clients.
It comes as the company ramps up its Brexit contingency planning.
"As we announced in 2017, Barclays will use our existing licensed EU-based bank subsidiary to continue to serve our clients within the EU beyond March 29 2019 regardless of the outcome of Brexit," the bank said.
"Our preparations are well-advanced and we expect to be fully operational by March 29 2019."
The move is designed to deal with the consequences of a no-deal hard Brexit, in which UK-based banks would lose passporting rights that allow them to function in the EU's single market, the world's richest trading bloc.
In approving the move, Mr Justice Snowden said in his judgment: "Due to the continuing uncertainty over whether there might be a 'no-deal' Brexit, the Barclays Group has determined that it cannot wait any longer to implement the scheme.
"In light of the large volume of business to be transferred, the scheme contains a number of phased dates upon which the transfer of the different types of business, and the business of the branches in Spain, Italy and France, will become effective.
"The overriding requirement, however, is that BBI (Barclays) must be legally and operationally ready to conduct all relevant regulated business with the in-scope clients by no later than March 29 2019, which is the date currently set for Brexit."
Several banks - including the Royal Bank of Scotland, Lloyds, Goldman Sachs, Morgan Stanley and a host of others - have set up continental hubs in preparation for Britain's exit from the EU.
This involves hundreds of jobs and hundreds of billions in assets being shifted out of London, hitting the UK Treasury's tax revenue and denting the city's reputation as a financial centre.
Frankfurt, Germany's financial capital, is one of the biggest beneficiaries of Brexit.
For its part, Barclays will increase its Dublin headcount by around 150 to 300 as a result of Brexit.