The transition from face-to-face trading in pits to a full electronic
system took place in two phases. In 1986, as part of extensive
deregulation known as the "Big Bang," "...London became one of the
first financial centres to see trading move out of the pits, off the
market floor and on to the telephone.
This was achieved by using a screen-based electronic bulletin board
known as Seaq (Stock Exchange Automated Quotations system).
Trading is quote-driven: market makers 'quote' a share price,
effectively competing with each other to display the best prices."
Full electronic trading was introduced in 1997. "On October 27, 1997
the London Stock Exchange completed its electronic revolution in
trading when it replaced the Seaq system with Sets - Stock Exchange
Electronic Trading - for the top 100 shares.
Sets's electronic order book means trades are conducted less and less by telephone.
Instead, orders to buy and sell shares are displayed and matched on a
computer screen. This is designed to give a better picture of what is
happening in the market."
"London Stock Exchange" BBC News (October 30, 1999)
The move to an automated trading system occurred very quickly, going
from a proposal in January 1996 to being operational in October 1997.
"Officials Unveil Options for Trading System: London Exchange Moves
On" By Erik Ipsen, International Herald Tribune (January 13, 1996)
Additional articles you may find of interest:
"From UK coffee house to bourse?" By Joia Shillingford, BBC News
(December 21, 2004) http://news.bbc.co.uk/1/hi/business/4112403.stm
"Our History" London Stock Exchange (2005)
"Death of the floor trader" BBC News (April 30, 2001)
Search terms: London Stock exchange electronic