This excerpt taken from the NDAQ 8-K filed Nov 20, 2006.
NASDAQ believes that it makes the best partner for LSE from both a market structure and a business perspective.
NASDAQ has a market structure which is similar to that of LSE, with multiple competing market makers supporting highly efficient and deeply liquid electronic limit order book trading. In addition to order book trading, both NASDAQ and LSE support the ability of market makers and broker-dealers to carry out off-order book transactions under the same regulatory and trade reporting umbrella as for order book trades. In addition to securities listing and transaction based trading operations, both businesses provide market information services and develop financial products.
In addition, NASDAQ and LSE are similarly sized organisations with a long history and experience in providing international companies with access to domestic investors and capital.