This excerpt taken from the NDAQ 8-K filed Dec 11, 2006.
LSEs clearing services arrangements could make it difficult to make alternative arrangements in an efficient manner.
Clearing services for securities on the London Stock Exchanges markets are provided by LCH.Clearnet Ltd, a subsidiary of LCH.Clearnet Group Ltd, which is partly owned by a competitor of the London Stock Exchange. We understand that the London Stock Exchange has in place detailed contractual provisions designed to ensure the fair treatment of the London Stock Exchange and its customers by LCH.Clearnet. We understand that LCH.Clearnet is currently proposing to migrate all the cash equity markets for which it provides clearing services onto a single clearing system. If implemented, we believe that such a migration will make it more difficult for the London Stock Exchange to transition clearing services to other providers in the event that the London Stock Exchange believes such a transition is in its and its customers best interests.