The UK's Transport for London (TfL) has bought back the shares of Tube Lines in a £310m ($458m) deal.
The TfL deal ends the £30bn ($44bn) public-private-partnership of the private contractor and brings London Underground back under state control.
The deal is expected to be completed by the end of June.
TfL is expected to manage the maintenance of the Jubilee, Northern and Piccadilly lines from May.
Tube Lines provides repairs and upgrades for trains and infrastructure on three London Underground lines.