Do you know this man? (Credit: British Transport Police)
The victim boarded the DLR service at Royal Albert station at around 10.25pm on Monday, 17 October.
A man sat opposite her and started speaking to her. He then sexually assaulted her.
The woman challenged the man who then moved to a seat across the aisle from her and exposed himself in front of her.
Detectives have released images of a man they believe may have information which could help their investigation.
Anyone who recognises him is asked to contact BTP by calling 08000 40 50 40 quoting reference 691 of 17/10/22.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
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Tags: Beckton, Newham, Sexual Assault, Royal Albert