A man was punched repeatedly in the face as he waited for a train to depart from Leeds station.
Now officers investigating the assault have released CCTV images of a man who they believe could help with their inquiries.
The assault happened at 11.15pm on Tuesday, March 26 on board a Leeds to Ilkley service that was waiting to depart from platform 2C.
A British Transport Police spokesman said: "A man is reported to have punched another man in the face multiple times. The suspect was removed from the train by members of the public. He then left the station.
"Officers believe the man in the images may have information that could help their investigation."
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Anyone who recognises the man pictured is asked to contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference number 1900024294.
Alternatively, call Crimestoppers anonymously on 0800 555 111.