Huntley is guilty. But still only he knows why he killed Holly and Jessica

Ian Huntley started two life sentences for the murders of Holly Wells and Jessica Chapman last night as an inquiry was launched into how he got a job as a school caretaker despite being investigated by police over a string of sex allegations, including four rapes.

Sixteen months after he dumped and burnt the 10-year-olds in a ditch, the "calculating and callous" murderer was found guilty on a majority verdict. When his minimum sentence is set by a High Court judge early in the new year, Huntley - accused by the prosecution of luring the girls into his home for sexual purposes - will be among the first prisoners in Britain to automatically spend the rest of his life in prison.

As David Blunkett, the Home Secretary, announced an independent inquiry into the vetting services provided by both Cambridgeshire and Humberside police forces to employers, it emerged that the 29-year-old had been accused of sexual offences nine times in his home town of Grimsby. Between 1995 and 1999, he had been accused four times of rape, once of indecent assault on a 11-year-old and four times of sex with under-age girls. All but one of the allegations were held in police files, but a series of blunders meant they were not provided to staff at Soham Village College.

Yesterday the former caretaker showed little emotion, simply shaking his head in a brief appearance of denial, as the jury of seven women and five men found him guilty of both murders after 18 hours of deliberations. His former partner Maxine Carr, 26, was equally unmoved as she was acquitted of two counts of assisting an offender, but nodded her head in apparent assent when she was found guilty of conspiracy to pervert the course of justice, a charge Huntley had already admitted. Holly and Jessica's former teaching assistant is likely to be free in five months, having already served half of her three and a half year sentence on remand. Her barrister, Michael Hubbard QC, said she would be blighted for years, facing an "unenviable future". Holly and Jessica's families, a dignified presence through every day of the seven-week trial, finally lost some of their composure as justice was delivered. Kevin Wells shook his head in agreement at the guilty judgments, and his wife, Nicola, wept.

Speaking afterwards, Jessica's father, Leslie, said: "Our life sentences started last August, his is only just beginning."

In sentencing Huntley, Mr Justice Moses said he had "enticed" the girls into 5 College Close, murdered them and destroyed the evidence. He said: "You showed no mercy and you show no regret. It is plain that once you killed one you had to kill the other in your attempt to avoid detection."

To Carr, he said: "Your selfish concern for yourself and Huntley led you to lie all too readily and all too glibly."

Huntley was driven back to the high-security Belmarsh prison in south-east London to begin his sentence.

Detective Chief Superintendent Chris Stevenson, who led the inquiry, said: "Only [Huntley] knows why he murdered Jessica and Holly. Perhaps one day he might demonstrate some sliver of humanity and explain why he did what he did that terrible day last August."

Mr Blunkett, announcing an independent inquiry headed by a senior civil servant, Sir Michael Bichard, said the investigation would look into how a police background check carried out on Huntley after his appointment in November 2001 failed to submit "intelligence" on the allegations against him.

The hearing, which is expected to take evidence from witnesses but will not have the powers of a judicial inquiry, will seek to establish whether the failure to keep a proper record on Huntley was a fundamental fault of the system or down to individual forces not following national guidelines.

The Chief Constable of Cambridgeshire, Tom Lloyd, said his force would give full co-operation to the inquiry, but he refused to discuss blame for errors in the vetting procedures or the handling of the murder hunt.

Humberside police admitted that the details on file about Huntley - including the sex allegations and one of burglary - had not been entered into the computer system because of the Data Protection Act, which the force insists bars it from recording unproved allegations.

An investigation was also announced by North East Lincolnshire social services into how it protected the four teenage girls at the centre of the allegations of under-age sex.

Huntley: cases reported to police

August 1995

Allegation of unlawful sexual intercourse with girl of 15. Girl's father alleged his daughter was having sexual intercourse with Huntley, which she admitted. Huntley interviewed, but the girl did not want the matter to go any further.

April 1996

Allegation of unlawful sexual intercourse with girl of 15 after her mother raised concerns. Police and social services investigated but girl did not co-operate.

May 1996

Allegation of unlawful sexual intercourse with 13-year-old girl. Police and social services interviewed girl, who denied sexual activity, supported by her mother. Huntley not interviewed; case dropped.

September 1997

Allegation of indecent assault on 11-year-old girl playing in orchard. She made the allegation 10 months later of an indecent assault by man called Ian. Huntley, who lived in same street, arrested but case dropped due to insufficient evidence.

April 1998

Allegation of rape on 18-year-old met in nightclub. Huntley claimed consensual sex. Woman gave statement, but police decided there was insufficient evidence.

May 1998

Allegation of rape on 18-year-old woman walking home from nightclub, who said attacker threatened to kill her. Huntley said sex was consensual. Charged, but after looking at CCTV footage, CPS ruled there was no prospect of a conviction.

February 1999

Allegation of rape of 17-year-old girl who went with Huntley to nightclub. It was not reported for three months. Huntley claimed sex consensual. Police ruled insufficient and inconsistent evidence.

July 1999

Allegation of rape on a 17-year-old as she walked home from nightclub. Maxine Carr provided alibi. Police decided not to proceed because of a lack of evidence.