Construction officially started in December 1993 and was expected to take 53 months. Tunnelling was delayed after a collapse during the Heathrow Express project in October 1994, which used the same New Austrian Tunnelling method. Indeed, construction under Westminster caused the Elizabeth Tower to tilt slightly. By November 1997 a September 1998 date was planned. By June 1998, opening was planned in Spring 1999. By November 1998, a phased opening, previously rejected, was being considered, with Stratford to North Greenwich planned for spring 1999, to Waterloo for summer 1999, and the link to the Jubilee line for autumn 1999.