Bank of America Merrill Lynch (BAML) has started its search for new office space despite the uncertainty of the City of London's future following the Brexit vote.
The US banking giant is currently located near St Paul's Cathedral, but as its lease expires in 2022, the bank has started looking at other buildings that could house its 1,200 bankers.
It is thought property agents at CBRE are involved in the survey for sites of around 500,000 square feet in size.
BAML is currently gathering information on potential new properties because it needs to make a decision on whether or not it stays in its current location by 2020. It started its property search before the EU referendum in June last year.
Even if the bank chooses to roll-over on its lease, it will need to have up-to-date information on the commercial property market to help it in negotiations with its landlord.
The news comes after it emerged that Lloyd's of London is making plans to ensure it maintains its access to the EU's single market. Lloyd's has said that it has been considering a subsidiary model and that possible locations for the move include Dublin, Paris and Frankfurt.
The firm's boss John Nelson said in 2016 that the company would leave the City if it didn't get passporting rights and that the firm has been making contingency plans because "it won't be Lloyd's losing out, it will be the UK".
Tech giant Apple, however, has decided to expand in London, despite the uncertainty surrounding the Brexit vote. In September, the company announced that it would be moving to offices in the Battersea Power Station development in 2021, a decision London mayor Sadiq Khan said showed "London is open to the biggest brands".
BAML and CBRE declined to comment.