A £700m project to revamp Victoria Tube station is set to begin after Transport for London (TfL) selected a contractor.
The central London station, used by 80 million people a year, will get a new ticket hall, entrances, escalators and step-free access to all platforms.
Vinci BAM Nuttall Limited, a joint venture, will begin the first phase of construction, a new ticket hall under Bressenden Place, in 2011.
The revamp, which aims to cut passenger congestion, will be completed by 2018.
The upgrade work will involve construction of a new North Ticket Hall, new entrances, expansion of the existing South Ticket Hall, step-free access to both Tube and national rail platforms, new lifts and escalators and a new passageway to the Victoria Line platform.
The project was first announced by the former mayor Ken Livingstone in 2007 but was only approved for funding by TfL last October.
Richard Parry, London Underground's strategy and commercial director, said the upgrade was "vital" and would help the station to "cope with future demand, cut congestion and improve access".
"This will be a huge benefit to residents, commuters and tourists, and customers will no longer face being held up by the station having to shut for several minutes in the rush hour because it is too full.
"It will also be much quicker and easier for passengers to enter and exit Victoria Underground station as they won't have to cross several busy roads."