By Rachel Grant
BBC News, London
The killer of 18-year-old Sally Anne Bowman was a serial sex offender who kept his past hidden from friends.
Police said Mark Dixie was "bad not mad"
Mark Phillip Dixie was first charged with indecently assaulting a woman when he was 16 and continued to get into trouble with police throughout his life.
Detectives investigating the murder of Miss Bowman said Dixie, who would not speak to them during the investigation, did not allow people to get close to him.
Det Supt Stuart Cundy said: "There is a lot we don't know about Mark Dixie. A lot of friends describe him as a normal person.
"As far as we know Mark Dixie has kept his history secret from just about everyone."
Dixie, a 37-year-old pub chef from south London, was "bad not mad", Det Supt Cundy added.
He was convicted of several offences in England during his teens and 20s, and was linked with a serious attack on a woman in Australia, where he lived from 1993 to 1999.
He lived in various parts of south London for most of his life, moving to Spain in 2002 and to Amsterdam in 2006.
He fathered three sons, two with the girlfriend he followed to Australia, and one with Stacey Nivet, with whom he lived in Croydon in 2003.
In court, Miss Nivet described him as the "life and soul of the party" when taking drugs, but said he suffered mood swings afterwards.
Det Insp Chris LePere said: "In life he seems to have been a freeloader. He used people and then moved on."
Over the years he is known to have used the names Mark Down, Mark James McDonald, Steven McDonald and Shane Turner.
Although he "showed no shame" during the murder trial, Dixie was in tears when Surrey Police arrested him in connection with a pub brawl at his workplace, Ye Olde Six Bells in Horley, and took a DNA swab.
But he did not attempt to disappear when he was released.
Det Supt Cundy said: "He's got away with stuff for so long around the world and he thought 'I'm invincible'."
It took two weeks for Dixie's profile to be added to the national DNA database. Five hours later he was arrested for murder.
Dixie's shocking defence - that he had sex with Miss Bowman's body after finding her dead - was a surprise to detectives when it was announced at the Old Bailey.
Det Supt Cundy believes Dixie denied murdering Miss Bowman because he wanted to enjoy re-living the attack in court.
Dixie's friends did not reveal he was in Croydon when Miss Bowman died
"Mark Dixie has made two of his victims re-live their ordeals at his hands in court and he has made Sally Anne's family sit through the most horrific evidence," he said.
Detectives believe Dixie, who had a tendency to "attack close to home", was responsible for an assault on a 36-year-old woman about an hour before Miss Bowman was killed.
When a cab driver came to the woman's aid, Dixie is thought to have run about 400m (1,300ft) to a "safe" place - Blenheim Terrace, the street in which he had lived with Miss Nivet.
Police believe that it was there that he saw Miss Bowman and her boyfriend Lewis Sproston having an argument in a car, and lay in wait, attacking moments after Mr Sproston left.
The Met believed they were looking for a local man, but Dixie's friends did not reveal that he was staying with them in Croydon on the night of the murder during house-to-house inquiries.
Police now believe it would have taken them two years for the inquiry to reach neighbouring boroughs and find Dixie without the DNA evidence.
Mark Dixie celebrates his 35th birthday at the Windsor Castle pub and then retires to a friends' flat in Avondale Road
Saturday 0300: 36-year-old woman attacked in Sanderstead Road
After 0415: Lewis Sproston drops Sally Anne Bowman off on Blenheim Avenue after a long argument in the car
0420: Sally Anne Bowman is murdered outside her house