A sadistic Ripper-style killer, jailed for life at the Old Bailey yesterday, faces further police investigations into other unsolved attacks on women throughout the UK.

David Smith, 43, described by the judge as ''extremely dangerous to women and likely to remain so'', murdered and mutilated 21-year-old vice girl Amanda Walker last April. He buried her in a shallow, leafy grave at a Surrey beauty spot frequented by lovers.

Six years ago, Smith - a martial arts expert who killed to satisfy his perverted sexual obsession - was cleared at the same court of the almost identical murder of another call-girl, Sarah Crump. His counsel had then accused police in court of suppressing evidence and incompetence.

Police emphatically denied the allegation. They closed the case, saying they were not looking for anyone else in connection with it.

Yesterday the Recorder of London, Judge Michael Hyam, told Smith it was evident that he killed Miss Walker ''to satisfy your perverted sexual obsession. You are without pity or remorse''.

Smith, from Hampton, west London, had denied murdering Miss Walker.

As the 6ft 3in, 18st lorry driver was led emotionless to cells, it emerged that police may now interview him about other unsolved attacks on women all over the country.

Miss Walker's body was found in a shallow grave near the Royal Horticultural Society gardens at Wisley, Surrey, nearly six weeks after she disappeared.

It was a spot renowned for sex romps and orgies. Miss Walker ''almost certainly'' was killed there by Smith, nicknamed ''Lurch'' by workmates because of his size and speech. He frequented the Wisley woodlands as a voyeur, watching others making love.

By day, Smith, a lorry driver, was a polite, softly spoken conscientious employee who kept himself to himself and lived with his mother. He had been married, but went back to his mother's home when a relationship failed.

By night he moved in a twilight world of prostitutes and sado-masochism. Although a convicted rapist, he ran his own escort agency - hiring girls out for #250 a time for sex, and banking a cut of their takings.

Smith picked up Miss Walker after attending a commercially organised ''party for broad-

minded adults'' in Ilford, Essex, said prosecutor William Boyce.

When he left, ''he felt randy and was looking for a bit of fun'', the court heard. Police say he wanted to control a woman totally. He went to Paddington, seeking out a prostitute. Here, Miss Walker, a newcomer to street life, crossed his path.

Smith had sex with her, killed her and later dumped her blood-stained clothing on a footpath a mile from his home.

Smith had already been arrested by the time her body was discovered. Police had trawled known sex offenders in the area where Miss Walker's clothes were found earlier. His DNA matched blood found on her clothing.

While in prison awaiting trial for Miss Walker's murder, Smith boasted of murdering her to his cell-mate, Stephen Williams.

It was his undoing, for tattooed Williams, himself a sex offender, was appalled by what he had heard and told police.

Smith told Williams that he had bound Miss Walker, wrapped her in polythene and cut her with a knife ''downstairs'' before and after having sex with her.

Smith, who knew the points of the body to put pressure on in order to inflict pain and kill, said he had put his hand on her nose and mouth. That was when she died.

Miss Walker was from a respectable family in Swarcliffe, Leeds, who had been trying to get her to give up her street life. Her relatives did not attend Smith's trial.

Miss Crump, originally from Lincoln, led a double life, working as a psychiatric nurse by day and for an escort agency at night.

Her body was found in her Southall, west London, home in August, 1991. She had been knifed and her dead, or dying body had been ''dreadfully mutilated''.

She was butchered in an almost identical pattern to operation scars borne by a woman Smith had once loved. That woman, known only as Janet, had rejected him. The prosecution at that trial in 1993 suggested that Smith murdered Miss Crump after this - and a series of rejections by women.

Yesterday Miss Crump's mother, Pat Rhodes, said that she always thought Smith would kill in the future. She sent condolences to Miss Walker's family.

When he was 20, Smith was convicted of raping a young mother in front of her two children. He served four years.

On his release, while working as an unlicensed mini-cab driver, he attacked a woman passenger after locking all the car doors. She escaped by kicking in the windscreen. Smith was charged with unlawful imprisonment and received a suspended sentence.

He was later charged with attempting to rape and stab a prostitute in a hotel room with a craft knife. But the woman failed to turn up at his trial to give evidence.