London Underground (Safety Measures) Act 1991

13Power to deviate

In the execution of any of the works shown on the deposited plans, the Company may deviate from the lines or situations thereof shown on the deposited plans to the extent of the limits of deviation and may deviate vertically from the levels shown on the deposited sections to any extent upwards not exceeding 3 metres and to such extent downwards as may be found necessary or convenient.