London - based banks could face " nightmarish " decisions if they lose access to euro - clearing trading , according to the Japanese Ambassador to the UK . Since 1999 , London has acted as the centre of euro - clearing for derivatives , but countries in the EU27 see it as unacceptable that the main clearing house should be located outside of the EU following Brexit . But he knew businesses were starting to research different scenarios. Business , in that case , would be likely to transfer to London and Paris .
London - based banks could face " nightmarish " decisions if they lose access to euro - clearing trading , according to the Japanese Ambassador to the UK . Since 1999 , London has acted as the centre of euro - clearing for derivatives , but countries in the EU27 see it as unacceptable that the main clearing house should be located outside of the EU following Brexit . Business , in that case , would be likely to transfer to London and Paris .