A man had his eye socket fractured when he was hit by a bottle during an attack in Leytonstone.
It happened close to the car park in Harold Road at 5.45pm on New Year's Eve, although details have only been released now.
Police say the 34-year-old victim's son had earlier that afternoon been approached by three men in a nearby takeaway.
When the man later spotted the group in Church Lane he went up to them to speak about the conversation.
He then went to his car and drove round the corner to Harold Road, where he got out.
But the three men followed him, ran up and hit him with the bottle before making off.
A Met spokeswoman said: "The suspects are all males, aged between 16 and 20 years and are believed to be Somalian.
"We are appealing for anyone who may have witnessed this assault to contact police.
"Contact DC Lee Nelson on 020 3276 0966. If you wish to remain anonymous contact Crimestoppers on 0800 555 111."