Today marks 20 years since Soham schoolgirls Holly Wells and Jessica Chapman were murdered by Ian Huntley.
He lured the two 10-year-olds to his home and killed them after they left a family barbecue to buy sweets in Soham, Cambridgeshire, on 4 August, 2002, then dumped their bodies in a ditch.
Huntley is serving a life sentence for their murders. His then-girlfriend, Maxine Carr, was sentenced to three-and-a-half years in prison in 2003 after being found guilty of conspiring to pervert the course of justice for giving him a false alibi.
Local newspaper's breakthrough
Huntley had previously been investigated for rape and underage sex with girls prior to moving to Cambridgeshire.
He had allegedly targeted young girls in the mid-1990s while living in Immingham and in Grimsby, North Lincolnshire – but there was insufficient evidence to convict him.
Social services investigated complaints and Humberside Police were involved in some of those investigations and also looked into three separate claims by women who said Huntley had raped them, but he was never convicted.
Huntley's criminal activity was never spotted by his college employers in Cambridgeshire when applying for the role in 2001.
The crucial breakthrough came when he appeared on television screens being interviewed about the schoolgirls after they went missing, in which he spoke about where he claimed to have seen them walking before they vanished.
Watch: Journalist recalls Soham killer's suspicious answers 20 years on
However, that appearance made a local newspaper reader suspicious.
At that point, police had gone 12 days without a suspect, but the reader recognised Huntley from the television interviews and knew of his background.
They called the Grimsby Telegraph and said journalists working at the paper should check their archives – whereupon the information about Huntley came to light and was passed on to detectives in Cambridgeshire.
Huntley's suspicious answers in an interview with another journalist also led the reporter at the paper to go to the police with his concerns.
On 17 August, Huntley and Carr were arrested on suspicion of abduction and murder.
Huntley, now 48, is serving a life sentence for the murders and Carr was sentenced to three-and-a-half years in prison in 2003 after being found guilty of conspiring to pervert the course of justice for giving him a false alibi.
He must serve a minimum term of 40 years before he is eligible for parole – when he is 68 years old.
Huntley managed to avoid the mandatory sentence of a full life term due to the passing of the Criminal Justice Act 2003 one day after his conviction.
He is an inmate at HMP Frankland in County Durham, having been moved from HMP Wakefield in West Yorkshire in 2008 after he was attacked by serial killer Mark Hobson.
Former teaching assistant Carr, now 45, has been given a new identity and police protection since her release in 2004.