The victim, 52-year-old Joy Hewer, was killed in her flat at St David’s Court 30 years ago.
Police said there were no signs of forced entry to the sixth-floor property, suggesting she may have known her attacker.
Her body was found in her bedroom after police were called to two deliberate fires.
Met Detectives are continuing to explore all opportunities in their investigation using modern forensic methods.
This includes analysis of a profile using advancements in DNA technology.
The Met is offering a reward of up to £20,000, for information leading to the identification, arrest and prosecution of the person(s) responsible for her murder.
Now Ms Hewer’s younger sister is appealing for help, as she paid tribute to a “gentle, caring woman” – saying the family now ‘deserves peace’.
Penny Barnes, 72, of Bedfordshire, said: “Thirty years ago, my sister Joy was brutally murdered in her own home.
“She was a gentle, caring woman who hurt no one, yet her life was taken in the cruelest way.
“Our family has lived with this torment for three decades, and our parents died without ever knowing the truth.
“Someone out there knows what happened. Please, after all this time, do the right thing. Even the smallest detail could finally bring justice for Joy and peace for us, her family.
“If you know something, however small, now is the time to speak up – Joy deserves justice, and her family deserves peace.”
Detective Constable Murray Bannister, from the Met’s Cold Case Homicide Team, said: “We urge anyone who might have information about what happened to Joy 30 years ago to contact police.
“A full DNA profile was recovered from the scene and we are continuing to explore all opportunities, including advancements in DNA technology.
“It may seem a long time ago, but three decades have not dulled the pain that this horrific act inflicted on her family. They are still fighting to get her justice, and we continue to use every means available to catch her killer.”
Joy, a devout Christian, was 52-years-old at the time of her death.
She had worked as a “much-loved” primary school teacher, most notably at nearby Woodhouse Primary School.
After retirement she worked relentlessly to raise money for local charities and church organisations.
Following numerous police appeals detectives were able to piece together Joy’s last movements.
Joy visited the London Healing Mission, in Notting Hill, on the afternoon she was murdered.
She carried out voluntary work at the Centre and was seen by a colleague leaving the Mission at around 3.30pm
She headed towards Pembridge Road before visiting a chemist close to her home address in Wood Street, Walthamstow at 5.50pm
A neighbour at St. David’s Court confirmed hearing loud noises or banging coming from Joy’s flat between 10.30pm and 11pm.
At 11.18pm on October 17, 1995 a phone call was made from a public telephone box along Fulbourne Road, Walthamstow.
The male caller was requesting assistance from the London Fire Brigade, having seen smoke coming from Joy’s flat.
Police made numerous appeals to trace this caller, previously releasing his 999 call in an effort to locate him.
He is still being sought as part of the investigation as he could hold vital clues.
While on the phone, the caller can be heard asking someone what road they were standing in to assist the emergency call handler.
According to police, he was actually speaking to someone, not known if male or female, who was standing in a queue for a bus.
The bus stop would have served buses heading to Walthamstow Central (212) and to Leytonstone Station (W16). This person is also yet to be located.
The Met has also issued an image of a man they would like to find.
He was captured on CCTV entering the front of St David’s Court at around 10.30pm on the night Joy was murdered.
He was described as white, in his 30s and with short hair.
He was wearing a light-coloured jacket.
Police were originally called by the London Fire Brigade at 11.45pm on Tuesday, October 17, 1995 to reports of a blaze at a sixth floor flat.
Firefighters broke into the premises and discovered Joy’s injured body in the bedroom of her E17 flat.
Two smouldering fires, deliberately started in the bedroom and another in the lounge, had to be extinguished.
A post-mortem-examination revealed the cause of death to be multiple injuries, including a number of stab wounds her chest.
The pathologist also indicated that Joy had been sexually assaulted prior to her death.
Anyone with any information is asked to the Met on 07599822129, or, to remain anonymous, call Crimestoppers on 0800 555 111.
