An NHS Test and Trace worker was knocked unconscious and repeatedly stamped on after moving away from a passenger on a bus who was not wearing a face mask.
The 63-year-old was punched to the floor of the vehicle in North London before his attacker – believed to be in his early 20s – stamped on his head five times.
So vicious was the unprovoked assault, the victim woke up in hospital with no memory of what had happened preceding the incident.
Police are now hunting the suspect and have released CCTV footage of the attack in a bid to identify him.
They say he boarded the 149 bus near Seven Sisters station shortly after the older man at 9.45pm on Sunday 23 August.
When the latter moved down the bus to put socially distanced space between them, the suspect – whose mask was hanging below his chin – followed. After an apparent exchange, he then launched the frenzied onslaught.
A spokesperson for London’s Metropolitan Police said: “Although there is no sound on the CCTV and all the victim remembers is waking up in hospital, we believe that this was all triggered by face masks.
"We think that the attacker, who had his face covering beneath his chin, took offence when the victim, who was fully covered, consciously moved away from him.
“When the attacker then follows the victim to the back of the bus, he can be seen pointing and gesturing at the victim’s face mask before he starts repeatedly punching and kicking him.
"This was a totally unwarranted violent assault and we urgently need to speak to this man.”
They described the suspect as black, aged about 23-25, tall and with an athletic and muscular build. He was wearing blue tracksuit bottoms, a white vest and white trainers.
Anyone with information is asked to call detectives on 07880 429 486, police on 101 or Crimestoppers anonymously on 0800 555 111.