British Transport Police officers want to speak to this man about an assault that took place on board a train at Hope station in Derbyshire.
Officers believe he could have vital information about what happened.
The incident occurred at around 11.15pm on Friday, August 14.
Investigating officer PC Joseph Robinson from British Transport Police said: “The victim was asleep when a man sat next to him. “The man then began to argue with a couple who were sat across from him.
“He then turned and hit the victim in the face with his walking stick which caused bruising and bleeding to his nose.
“This was a completely unprovoked attack which left the man bruised and bloodied. Violence like this will not be tolerated on the railway network.”
Officers are urging the man in the CCTV image, or anyone who recognises him, to come forward in order to assist with their enquiries.
Anyone with information about the incident is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference PSUB/B8 of 09/09/2015.
Information about the incident can also be passed on anonymously to Crimestoppers by calling 0800 555 111.