At around 9pm on Tuesday 7 March, the victim boarded the train at Sandhills station where he was confronted by a stranger who punched him several times.
Another passenger who attempted to intervene was also threatened by the man, who boarded the service at Cressington station at 8.42pm.
Anyone who recognises him is asked to contact BTP by texting 61016, or by calling 0800 40 50 40 quoting reference 590 of 07/03/23.
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