Ahead of Brexit, Deutsche Bank AG, Commerzbank AG and 15 other lenders conducted a dry run of a service that could move derivatives worth trillions of dollars from London to Frankfurt, insiders told Bloomberg News.

The lenders tested moving derivatives from London Stock Exchange Group PLC's LCH Ltd. in London to Deutsche Börse AG's clearing arm Eurex Clearing AG in Frankfurt. If the U.K. leaves the European Union with no exit deal in sight and the lenders have to access the service, the bank's existing position in British clearing house LCH will be lost, with new positions opening at Germany's Eurex Clearing.

The EU will allow derivatives traders to access U.K. clearing houses up to a year in the event of a no-deal Brexit. EU states agreed that so-called equivalence rights should be given to companies for the period of a year, starting "day one" of Brexit, to give them time to adapt to the changes that may come with the move.

Currently, euro-dominated derivatives clearing is dominated by LCH and is concentrated in London.