In the case of a Brexit, let’s replace British Clearing Houses with FinTech

Blockchain model (left) vs. a central clearing house model (right) Source:

In our time, technology is powering new solutions to seemingly distant problems. Facilitating around 1 trillion euros worth of transactions every day, The U.K. and its clearing houses dominate the European OTC (Over The Counter) transaction market. Back in 2011, the European Central Bank considered this a systemic risk, and tried to lower the market share of transactions handled by the U.K. but failed.
Part of what the E.U. wanted to hedge is happening through Brexit. Contingent upon the U.K leaving the E.U, all clearing and settlement activities will be forced to go back the continent. Clearing, however, doesn’t have to go from British entities to European ones. In a measure that can be implemented quickly and which will also substantially cut costs, enhance transparency, and boost speed of transactions – the E.U. can use Blockchain technology. 
By definition, clearing is the process of matching buyer and seller records to complete an agreed-upon transaction. The underlying technology of Bitcoin, Blockchain, serves a similar purpose.  Through cryptographically secured methods, the Blockchain gives every new transaction (block) a stamp that links it to all previous transactions (chain) and so on. And because there is no central authority to maintain such a ledger, The Block Chain is maintained by the parties (computers) that use it, the latter are called “nodes”.  For example, every transaction that has ever occurred in the 7-year history of Bitcoin can be found and traced back, and the IDs of the buyer and seller identified, without referring to any central or intermediary organization. 
Similar implementations are already being applied, startups like Counterparty bypass clearing and allow users to manage assets and exchange them through a BlockChain. All E.U. officials would need to do, on a practical level, is to replicate these models. 
Questions may rise about scalability but the quickest look into the Blockchain refers to Bitcoin, which once went from a market capitalization of $0 to $14 billion, and a daily transaction volume of 0 to around $6 million USD at its peak (source
Most shifts in international transaction mechanisms happened through political shocks: WWI gave us Bretton Woods and Nixon cancelling the dollar’s gold convertibility gave us today’s floating exchange rates system. A Brexit could be an opportunity to introduce the world to a new era of decentralized asset management, powering increased speed and transparency at a fraction of today’s costs, cancelling all together the role of clearing houses.