Dame Barbara Mills, a former head of the UK's Serious Fraud Office, is to investigate the proposed bids for the London Stock Exchange from Deutsche Börse and Euronext. She is one of four members of the Competition Commission who will work with Paul Geroski, the watchdog's full-time chairman.

Mills, who was also director of public prosecutions, will be joined by Jeremy Seddon, who headed the privatisation unit of BZW, the investment bank owned by Barclays, before becoming chief executive of British Invisibles, a body that promoted City of London services such as the London Stock Exchange abroad.