Police are searching for a mugger who knocked a 92-year-old man to the ground and grabbed his wallet before fleeing with just £10.
The frail pensioner told ITV News he would have fought back if "he was fitter".
The pensioner was attacked in the communal entrance of the block of flats where he lives alone in Soho, west London, after the attacker followed him through the door.
The Metropolitan Police, who called the mugging "sickening", have issued CCTV that shows the robber taking the wallet before leaving the victim stricken on the floor. He remained there for five minutes before managing to get to his feet and take a lift to his flat to dial 999.
The man, who lives alone, suffered a shoulder injury in the attack. He did not need hospital treatment, but police said he was "living in fear of his safety."
The suspect is described as a black man, between 5ft 10in and 6ft, slim and aged 20-30. He appeared to be wearing casual dark clothing.
Detective Sergeant Gemma Alger of the Westminster Serious Crime Unit said: "This is a totally unprovoked, callous and sickening assault on a defenceless pensioner.
"The victim is fiercely independent and has lived in London all his life. His confidence has been eroded as a result of the actions of this individual and now he is fearful about going out.
"I would urge anyone who has any information on who was responsible to contact us as soon as possible before he targets someone else."