Private companies that are keen to trade their shares but do not wish to become listed have gained another way to trade their shares via the new U.K. regulatory framework, the Private Intermittent Securities and Capital Exchange System (PISCES). The U.K. government completed its initial review and published rules for the system in June. 

Ruth Prickett graduated from Cambridge University with a BA hons in History and has specialized in business and finance journalism for the past 20 years. She was editor of Financial Management, the magazine...