Barclays Bank has spent £100-200m on its Brexit preparations, which has seen it shift hundreds of billions of euro in assets to its Dublin offices.
The bank's chairman Gary Grimstone said its expanded Dublin operations, which will manage its network across Europe, will be "completely open for business" on March 30.
"It will have a balance sheet of almost €200 billion of assets, making us one of the largest Irish banks," he said.
"1,700 bankers on the continent will work directly for this business here in Dublin," he added.
Speaking at the European Financial Forum in Dublin today, Mr Grimstone said Brexit has seen the UK go from being one of the most predictable places in the world to do business in, to one of the least predictable.
He said there would need to be a "high priority on restoring that predictability" once the outcome of Brexit was known.
The Barclays chairman said the process had made people like him, who built a career trying to predict things, "almost lost for words".
Mr Grimstone also expressed admiration for what he described as British prime minister Theresa May’s "tenacity" in trying to get a Brexit deal through.
However he said that Britain had spent the last two years trying to reconcile two very different views, with the debate focusing on how the country could leave Europe's Customs Union while also staying within it.
He said Brexit presented a challenge for Barclays but his philosophy had been to embrace this and see what opportunities it created.
The company's Dublin office, along with an expanded trading presence in Frankfurt, would help it to become a major force in the euro market going forward, he said.
He also complimented Irish authorities for making the process of scaling up its Dublin office "as smooth as possible" over the past two years.