A spokesman for Greater Manchester Police said: "There is nothing to suggest that this wasn't an unprovoked attack.
"The woman has been grabbed, thrown to the ground and the offender has banged her head against the ground, causing injury.
"We have been given a description of a man who was black, 5ft 9in, skinny, and wearing a red hoodie with the hood pulled up and black tracksuit bottoms.
"He is suspected of the assault, but there may be nine other people involved."
Inquiries are ongoing and officers are examining CCTV footage of the attack.Could it be because they sometimes show things in a rather different light?
Something to ponder.