A man was seen headbutting a woman on the corner of London Road and Windmill Road in Headington.
The incident happened at about 10am on Tuesday, June 24, but Thames Valley Police only released details yeterday.
They believe a number of people at a nearby bus stop may have witnessed the assault and know that at least one woman asked the victim if she was okay.
Police have descibed the man as white, of large build and with short blond hair and he was wearing a red T-shirt and dark trousers.
Police want witnesses to contact Detective Constable Vicki Middlecote by calling 101.
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