The most complex and technically demanding station on the jubilee Line Exte
nsion Project, with the deepest basement in London, was constructed within
the political heart of the country and under one of London's oldest undergr
ound railway stations. Various civil engineering techniques such as tunnell
ing, piling, diaphragm walling and top-down construction were used to const
ruct the station escalator hall and foundations to a prestigious new parlia
mentary building. Buildings surrounding the worksite, together with the Dis
trict and Circle Line station passing diagonally through it, severely restr
icted construction access and working space. Major challenges to the constr
uction team included movement control of adjacent structures such as St Ste
phen's ClockTower (Big Ben) and a major trunk sewer, and rebuilding the exi
sting station while maintaining an uninterrupted flow of passengers and tra
ins through the station. This paper describes the construction of the new W
estminster Station (excluding tunnel works), which was part of Contract 102
of the jubilee Line Extension Project: Green Park to Waterloo Tunnels, Wes
tminster and Waterloo Stations.