Construction works began in 1962. The 1930s ticket hall under the roadway of Piccadilly was enlarged to provide space for new Victoria line escalators and a long interchange passageway was provided between the Victoria line and Piccadilly line platforms. In 1965 a collapse of soft ground during the excavation of one of the tunnels near Green Park station meant that the ground had to be chemically stabilised before work could continue. The disused station building in Dover Street was demolished the following year in conjunction with the works for the new line. A vent shaft was constructed and an electrical sub-station was built in the basement of the new building. The 1930s entrance on the south side of Piccadilly was also reconstructed.