The British Transport Police were called to Mile End Underground station in Mile End Road at around 11.30pm on July 20 with reports of an incident.
At the scene a man was found injured after being assaulted at the ticket line.
He was taken to a major trauma centre with a head injury, which is not believed to be life-threatening or life-changing.
A London Ambulance Service spokesperson said: “We were called at 11.26pm on Sunday 20 July to reports of an assault on Mile End Road, E3.
“We sent resources to the scene, including an ambulance crew, an incident response officer and a paramedic from our tactical response unit.
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“We also dispatched a trauma team in a car from London’s Air Ambulance, which consisted of a paramedic and a doctor in a car.
“We treated a man for a head injury and took him to a major trauma centre as a priority.”
Anyone who witnessed anything or has information is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 648 of 20 July.
