Police believe that the man in this CCTV image may have information about a vicious attack on a train that was headed for Colchester.
A man was taken to hospital after the assault, which left him unconscious.
The man, who is in his 50s, was attacked while on a train from London Liverpool Street to Colchester.
He was waiting for the toilet when he was punched in the head by another passenger.
He fell to the ground, where the attacker then stomped on his head.
As a result of the attack, the victim was left unconscious and required and overnight stay in hospital.
He sustained a number of bruises to his head, legs and arms.
The assault happened onboard a Greater Anglia service which had just departed Liverpool Street station.
Officers from the British Transport Police (BTP) believe the man shown in this CCTV image may have information which could help them investigate the incident.
They are asking anyone with information about the attack to contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 31 of 10/11/2018.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here