London Stock Exchange (LSE)

The LSE is completely electronic, but different shares are traded on different systems. Highly liquid shares are traded using the SETS automated system on an order driven basis. This means that when a buy and sell price match, an order is automatically executed. For securities that trade less regularly, the London Stock Exchange implements the SEAQ system, where market makers keep the shares liquid. These market makers are required to hold shares of a specific company and set the bid and ask prices, ensuring that there is always a market for the stock.
The LSE also has a new and growing exchange for equity derivatives called EDX London, created in 2003. In 2004, EDX traded an average of 382,599 contracts per day. Its aim is to become the leading derivatives market in the world.