The London Access Lift has stairs that raise and lower vertically thus removing the requirement for a pit behind the top step riser.
The top step riser is not a moving stair, it is formed as part of the upper landing area. For example, a staircase with 6 risers will have 5 vertically retracting stairs that will lower.
When the stairs lower the surrounding stair profile will be revealed. Typically this is clad in stainless steel as it is not seen when the stairs are in their rest position. This side stair profile houses a locking mechanism that stabilises and supports the stairs when they are in their rest position.
Please see retracting stair technical page for more information.