An NHS Test and Trace worker was savagely beaten in an attack "triggered by face masks".
Police are searching for a man who allegedly put the 63-year-old health worker in hospital after attacking him on a bus in north London.
Scotland Yard said in a statement that the victim boarded the route 149 bus just before Seven Sisters station, with his alleged attacker getting on board at the next stop at about 9.45pm on August 23.
About five minutes later he was allegedly punched repeatedly to the floor and had his head stamped on five times during the attack.
Pc Bowman from the Roads and Transport Policing Command 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.”
The alleged attacker is described as a tall black man aged approximately 23-25 years with an athletic/muscular build. An image has been released by police of a man wanted in connection with the attack.
Anyone with information is asked to contact detectives on 07880 429 486 or on 101, quoting ref CAD 7981/23Aug.