This happened on Monday 20 October 1997, on which day the London Stock Exchange introduced a new computerised dealing system. The term is derived firstly from the original financial Big Bang of 11 years earlier, when the Stock Market was deregulated and a new electronic dealing system called SEAQ (Stock Exchange Automatic Quotation System) was introduced. Both terms are punning references to the cosmological Big Bang because of the fundamental changes that deregulation has brought to the traditional structure of share trading in the City. The new system, which the Chancellor of the Exchequer formally inaugurated, takes electronic trading a step further by implementing an order-driven approach, automatically matching buying and selling orders for shares of the 100 largest firms, bringing London’s dealing systems in line with others around the world. For these shares it replaces the older market-driven system operated by market makers who have been setting prices since the first Big Bang. If it works well it may eventually be extended to all shares.