At a press conference yesterday, detectives said they believed burglary may have been a motive after witnesses reported seeing a garden door open which the assailants could have used to gain entry to the house.
The battered, bleeding and semi-naked body of Mrs Williams, 29, an unemployed stage manager, was discovered in her home in Dockhill Avenue, Surrey Quays, Rotherhithe, by her husband Tim, 31, also a stage manager, soon after 2am on Sunday when he returned from working in Plymouth.
One man was seen at 1.45pm on Saturday afternoon. He was described as white and wearing a grey long-sleeved pullover. He was seen jumping up and down and knocking on the front door. He was also seen sitting on the front doorstep for two or three minutes.
A second man was sighted by witnesses between 1.10pm and 2pm that afternoon, looking over the back garden fence while standing on a rock. Police describe him as 5 ft 9 in, of Mediterranean appearance, and athletic build with black hair, cropped short at the side and gelled on the top. He wore a dark blue or black baggy bottomed shell suit. He had a few days growth on his face. He was seen carrying a very dark bottle green jacket made out of a silky material. Both men are though to be in their twenties.
Detective Superintendent Gordon King: 'It would seem that she had left the back door open that leads into the garden. This has been confirmed by a neighbour.
'Her husband has said that she was used to using the back garden as an extension of her kitchen on a hot afternoon. It could well account for the reason why the suspects were able to make their way into the premises.
The family of Mrs Williams are said to be absolutely devastated by the murder. Her husband Tim, his parents, the victim's parents and brother are understood to be together in London.
Neighbours on the estate had previously complained of prowlers in the area.
Detectives have now narrowed the time of the murder to between 11.30am and 3pm on Saturday afternoon.
The last person to speak to her was her father who telephoned her at 11:30am on Saturday.
He said she sounded happy and was looking forward to her husband's return. Mr Williams had called at 3pm but got no reply and left a message on the answering machine.