A thug stamped on a woman's head and robbed her of just £20 while witnesses filmed the attack on their smartphones.
The 45-year-old victim was rushed to a south London hospital after suffering a fractured skull and a broken arm. Police say she is still recovering from the assault that took place in broad daylight in Brixton on 15 December.
The early afternoon attack on what officers describe as "a vulnerable woman" was filmed by a number of witnesses who shared the incident on social media.
Detectives said the woman was approached by a man who demanded money from her and repeatedly stamped on her arm and head before taking "no more than £20".
The man was described as a light-skinned black man, with a dark hooded top, a bottle-green gilet and dark tracksuit trousers.
Scotland Yard has now released a CCTV still image of the suspect – which it admits is a low resolution picture – but "hopeful" it will provide clues to identifying the assailant described as "a danger to the public".
Detective Constable Nicky Dixon, from Lambeth CID, said: "This was a brutal attack of a vulnerable woman in broad daylight. She was unable to defend herself and was left semi-conscious on the ground with serious injuries which required emergency treatment.
"We know the assault was witnessed by people who have not come forward and I would urge them to speak with us.
"This man is a danger to the public and needs to be caught – someone knows who he is and I appeal to you directly for your help."
Anyone with information is asked to contact officers on 07785 774447 or via @MetCC. Alternatively, they can call Crimestoppers anonymously on 0800 555 111.