The Transport for London (Arlington Street) Order 2004
Section 163 of the Greater London Authority Act 1999 prohibits Transport for London from granting a leasehold interest in operational land for a term of more than fifty years without the consent of the Secretary of State. Under section 164 of that Act Transport for London is required to ensure that none of its subsidiaries does anything which Transport for London has no power to do (including anything which Transport for London has no power to do because the consent of the Secretary of State has not been obtained).