A reward of £20,000 is still on offer for information leading to the identification, arrest and prosecution of those responsible for the death of 81-year-old Molly Morgan.
Mrs Morgan was attacked at around 7:40pm on Thursday, 15 January 2009 as she was on her way to Kenton Library to a lecture called 'Buildings in London'.
She had walked about a mile from her home to Streatfield Road, Harrow, when she was attacked.
Her handbag was pulled from her and she fell to the ground, hitting her head and the left side of her body. She was taken to Northwick Park Hospital where her condition deteriorated and she died the following day.
Mrs Morgan had suffered a broken left arm and multiple fractures to the left side of the face consistent with a fall. A post-mortem examination gave cause of death as subdural haematoma.
Her brown leather-effect shoulder bag which was stolen contained only an empty Sainsbury's carrier bag, an electrical extension lead and a brown and gold Primark umbrella.
The extension lead and handbag were seen in Northwick Avenue, Kenton near to the junction with Rushout Avenue, at 21:00hrs on the night of the murder. Only the extension lead was recovered by a resident the following day, the handbag had disappeared and has never been traced.
Witnesses saw two men/youths running along Streatfield Road towards Kenton Library immediately after the attack on Mrs Morgan.
A man wearing grey jogging bottoms was seen walking ahead of Mrs Morgan in Streatfield Road - appeals also continue to trace this person.
Detective Chief Inspector Andy Partridge, of the Homicide and Major Crime Command, said: "It is now six years since Mrs Morgan was murdered and despite extensive enquiries we have never been able to bring her killers to justice.
"She was an active and highly respected member of her local community and she was killed for essentially an empty handbag.
"A substantial reward is still available for information that brings the perpetrators to court and we hope that with the passage of time someone who did not feel able to come forward before may now have the confidence to approach police."
Mrs Morgan had lived in the local area for more than 50 years and was very agile and active in the local community. A member of the Royal Horticultural Society, she had an allotment locally. She sat on the London committee of the Worker Education Association, a group supporting adult education.
She had originally trained as an architect but gave up work to become a full-time mother to her daughter.
She was married to William Morgan for more than 40 years. He died in November 1997.
Any witnesses or anyone with information is asked to contact the incident room on 020 8358 0300 or if you wish to remain anonymous, Crimestoppers on 0800 555 111.