Bankers in Canary Wharf have felt the impact of Brexit more immediately than most.
They are battling to cope with stocks plunging, the pound plummeting to a 31-year low against the dollar and the FTSE 100 losing £85billion.
Going forward the referendum result means banks may look to relocate away from London if the UK leaves the single market as well as the European Union.
Leaving the zone, also known as the European Economic Area (EEA), would mean the loss of “passporting”, which allows banks to operate without restriction in all member countries.
The head office of Barclays is in the 32-floor skyscraper at 1, Churchill Place in Canary Wharf.
Group chief executive Jes Staley said: “The United Kingdom has voted to leave the European Union.
“This is a significant decision and there will be many questions asked in the coming days and weeks about what happens next. The answers are complex but our position is not. We will not break our stride in delivering the Barclays of the future.
“We have stood in service of our customers and clients for over 325 years. We have been here for them through equally profound changes before. And no matter what has been laid before us, we have been here to help them achieve their ambitions.
“That does not change today. And through the uncertainty of the months ahead, be in no doubt that we are ready to do whatever it takes to uphold that promise.
“The strategy we announced on Tuesday, March, 1, 2016 was not conditional on the UK remaining in the EU.
“We are a transatlantic consumer, corporate and investment bank, anchored in the UK and the US. That remains the core of our strength.”
The head quarters of HSBC Group is in a 45-floor skyscraper in Canada Square, Canary Wharf.
It has declined to comment on reports it would move up to 1,000 staff from London to Paris if the UK left the single market.
In a statement it said: “We are entering a new era for Britain and British business. The work to establish fresh terms of trade with our European and global partners will be complex and time consuming.
“We will be working tirelessly in the coming weeks and months to help our customers adjust to and prepare for the new environment.
“As one of the largest, most stable, liquid and prudent financial institutions in the world, HSBC is well placed to support our customers and the markets as they deal with the challenges that will arise.
“Our commitment to British businesses, customers and staff in the UK remains undiminished.”
The European headquarters of JP Morgan are at 25 Bank Street in Canary Wharf.
A statement from parent company JPMorgan Chase said: “British citizens voted to begin a new, independent relationship with the European Union.
“This decision is a seminal moment in European politics and in the history of the United Kingdom.
“JP Morgan has 16,000 employees in the UK. We are extremely proud of the work they do and our long history in the country.
“We will maintain a large presence in London, Bournemouth and Scotland, serving local clients as we have for more than 150 years.
“The framework of the UK’s engagement with the EU, including trade agreements, will be negotiated over a period of years.
“For the moment, we will continue to serve our clients as usual and our operating model in the UK remains the same.
“In the months ahead, however, we may need to make changes to our European legal entity structure and the location of some roles.
“While these changes are not certain, we have to be prepared to comply with new laws as we serve our clients around the world. We will always do our best to take care of our people and do the right thing during times of change.
“We recognise the potential for market volatility over the next few weeks and we are ready to help our clients work through it. There are no changes to the structure of our clients’ relationships with JP Morgan Chase or their ability to work with our firm, but again this may change in the coming months or years.
“We are hopeful that policy makers will recognise the immense value created through a continued open economic engagement between the UK and EU members.
“As negotiations offer more clarity over the coming months, we will communicate with you and with our clients regarding any relevant changes.”