The extension was authorised in 1990. A station was originally planned at Blackwall, but this was replaced by diverting the line between Canary Wharf and Stratford underneath the Thames to serve the Greenwich peninsula at station. Plans for the Millennium Dome did not yet exist, and this diversion was made to provide for a planned housing development on the site of disused gasworks. British Gas plc contributed £25 million to the scheme. The stations at Southwark and Bermondsey were not initially certain. Main works were authorised by the London Underground Act 1992, with additional works allowed by the London Underground (Jubilee) Act 1993.