The westbound train platform at Ealing Broadway station was closed to passengers while emergency services dealt with an injured person.
A woman slipped down the stairs to the platform and injured her knee in such a way that she could not be moved, a spokesman for British Transport Police told getwestlondon.
The route down the stairs was blocked, which led to the platform being closed for around 75 minutes.
The woman was taken to hospital for treatment to her injuries.
The event was described as non-suspicious and lines returned to normal at around 8.30pm.
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