A man told a commuter he had a knife before headbutting him as he waited for a train.
The 46-year-old victim was attacked at Ilford station on March 16 when the man approached him shortly after 6.40pm and began shouting.
He claimed to have a knife and grabbed the rail user before assaulting him.
Police have released a CCTV image of a man they would like to speak to in connection with the attack.
Detective Constable Michael Hatcher, who is leading the investigation, said: “This was an unprovoked attack which left the victim needing hospital treatment for pain and swelling to the face.
“I urgently want to speak to the man pictured as we believe he has key information about what took place.”
Anyone with information can call British Transport Police on 0800 40 50 40, or text 61016, quoting background B8 of 11/04/201414. Alternatively people can speak to Crimestoppers anonymously by calling 0800 555 111.
