Accessibility
An increasing number of stations are becoming accessible. However, the network is old and some stations must be difficult to adapt. So many (eg Leicester Square) have steps from the platform (perhaps cost saving or flood prevention), narrow corridors, long escalators and more steps.
There are stations (eg Waterloo) where the track at the platform is so curved that there is a big gap between the train and the platform.
Other stations, especially the newer ones, are more accessible. There are raised platform sections to make level access, lifts (elevators), priority seats on platforms and trains and even ramps with staff to help.
Contact TfL directly if you have needs.