A three-year project to install new escalators at Marylebone Tube station is set to start later this month.
Transport for London (TfL) has warned passengers that the station will remain open while the two escalators serving the Bakerloo Line are replaced.
A third is set to be added too, TfL has said.
It added that the work will start on replacing the two existing escalators, which date back to 1943, one at a time, to reduce the impact on customers.
Esther Sharples, Director of Asset Operations at London Underground, said: “The escalators we’re replacing are some of the oldest on the Tube network and this is essential work that will improve journeys through Marylebone station for years to come.
"Once the work is complete, the station will have improved capacity and reliability, which is particularly important at this busy interchange.”