A 70-year-old dementia sufferer was left with head injuries after his Herne Hill home was raided by a man on Monday morning.
His wife, 58, discovered him with a nose injury and bruises to both eyes at their Fawnbrake Avenue address.
Two laptops and a mobile phone had been stolen from the property, and police have released a CCTV image of a suspect they are trying to trace.
DC Anne Hogarth, from Lambeth police, said they do not have a “full picture” of what happened as the victim suffers from short term memory loss and struggles to communicate.
She added: “I urge anyone who knows the man pictured in the CCTV or was in the area at the time to search their conscience and come forward. I am sure that they would feel disgusted if had happened to somebody from their own family.”
The CCTV image shows a man wearing a striped shirt, who police suspect entered the property at 9.13am and left nine minutes later.
Anyone with information on the incident should call Lambeth Serious Acquisitive Crime Unit on 020 8649 2153 or Crimestoppers anonymously on 0800 555 111.