A woman was at the station on August 17 just before 4pm when a man reportedly sexually assaulted her.
He then ran onto a train from Gants Hill heading to Stratford.
Nearly three months later, the British Transport Police has launched an appeal looking to find a man officers would like to speak to.
While there is not an actual image of him, police have put together an E-fit based on his description.
DS Gough said: ”Unfortunately CCTV footage of the incident was unavailable in this particular case, so we are releasing an E-fit of a person we would like to speak to in connection.
“We believe that the man may have information which could help our investigation and urge anyone who recognises him to get in touch.”
Anyone with information is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 349 of 17 August.
You can also contact Crimestoppers anonymously on 0800 555 111.
