In 2014, the United Kingdom cleared $927.8 billion Euro-denominated derivatives daily. France, the biggest rival cleared just 15.2 percent of that. The United States cleared less than 3 percent of that. Eurozone's three largest economies together cleared less than a third of what the UK cleared.

Go by any measure you like that number is mammoth. It would be a shame to lose that.

However, through this referendum, Britons have raised the prospect that EU members would try their best to take a bite out of that number.

One of the key priority for the new UK government will be to protect London so that the city remains the undisputed champ of the financial world.

Chart courtesy: Bank of International Settlements,Bloomberg , Financial Times