Without Big Bang - the deregulation of the London Stock Exchange that happened 20 years ago this Friday - it is doubtful if London would have retained its place as Europe's pre-eminent financial centre, and certain that it would not have become the foremost truly international financial centre of the modern globalised economy that it is today.

The story began in 1979. Nicholas Goodison, the chairman of the stock exchange, fearful of the cost of a long drawn-out investigation of its restrictive practices by the Office of Fair Trading, the competition body, and its inevitable outcome, asked the new Conservative government to call off the OFT in return for a promise that the stock exchange would reform itself.