An off-duty police officer was bitten on the face when he responded to an announcement for police help on a packed Tube platform.
The officer was attacked on the westbound platform of the Piccadilly Line at King's Cross station during the evening rush hour on Friday.
He was responding to a PA announcement requesting assistance after reports of a disturbance, police said.
Lompongo Yimbe, 30, was later charged with causing grievous bodily harm.
The officer received medical attention for a serious facial injury and has since been released from hospital.