Police believe Mrs Phillips was killed around 1100 BST on 14 June 1985

South Wales Police know customers had come and gone before she was brutally killed sometime around 1100 BST.

Her body was found by the store's area manager who made a routine call to the Dillwyn Street premises at 1345 BST.

It had been locked from the outside and Mrs Phillips' keys were missing and were never recovered.

Detectives found her body in a pool of blood and she had been doused in petrol.

Think about the family of Sandra Phillips who have lost a mother and a grandmother Superintendent Simon Clarke

A number of unidentified fingerprints were found at the scene and a telephone handset that was on the wall behind the counter was gone.

The Gwent Police Fingerprint Bureau will review all the prints found at the scene and a number of specialist forensic agencies will examine certain areas of the shop wall and floor.

Detective Superintendent Simon Clarke, who is heading the new investigation into the 38-year-old mother-of-four's death said he was confident advances in science, together with fresh witness statements, would help to finally solve the crime.

"There are grandchildren alive today in south Wales who have never seen their grandmother," he said.

"It's been 20 years of heartbreak and I have made a commitment to them that I will resolve this matter."

The current investigation team was appointed to the case in June 2004 - a year after it was re-opened as part of South Wales Police's policy of conducting independent reviews of unsolved cases.

Brothers Paul and Wayne Darvell were wrongly convicted of the murder and set free by appeal court judges in 1992.

The two were unemployed and had lived rough and in hostels in the area.

The Darvell brothers were wrongly jailed for the brutal murder

After hearing that a police notebook had been altered and that the brothers had a history of confessing to things they had not done, the appeal court ruled the convictions were "unsafe and unsatisfactory".

The brothers were subsequently awarded �80,000 each in compensation.

Earlier this year Paul Darvell, who was 42, died at his home in Neath.

Superintendent Clarke said as well as speaking to Mrs Phillips family he had also talked to members of the Darvell family who were supporting the new inquiry and keen to have the case solved.

"At 1100 BST on Tuesday (the 20th anniversary of Mrs Phillip's death) I would ask members of the Swansea community to have a quiet reflection.