The trial of Ian Huntley for the murder of schoolgirls Holly Wells and Jessica Chapman opened on Monday.
The girls went missing in August last year
The parents of the girls were at the Old Bailey as jury selection began in the case against Mr Huntley and his former girlfriend Maxine Carr.
Mr Huntley, a former school caretaker, denies murdering the 10-year-olds.
Ms Carr, 26, who worked at the school the girls attended in Soham, denies two charges of assisting an offender and one of conspiring to pervert the course of justice.
The girls' parents arrive for the start of the trial
The girls disappeared on 4 August last year after they had been playing at Holly's home.
Their bodies were found almost a fortnight later close to the RAF base at Lakenheath in Suffolk.
At an earlier court hearing Mr Huntley admitted conspiring to pervert the course of justice.
Mr Huntley and Ms Carr, who have been held in custody since their arrests on 17 August last year, were led up to the dock on Monday with a security officer between them.
Their trial will take place at the Old Bailey's Court number one and, after several days of legal argument, the prosecution is expected to deliver its opening statement on Wednesday.
Shortly after 1000 GMT, the parents of the girls walked the short distance from Snow Hill police station to the Old Bailey - Kevin and Nicola Wells holding hands.
Together with Sharon and Leslie Chapman, the two couples paused briefly for photographers outside the entrance to the court, before walking in.
Against the wall of the court building well-wishers had set up a small, impromptu memorial to the girls, with bunches of flowers and a wreath. Among the tributes was one from "Manchester United fans".
Stephen Coward QC will defend Mr Huntley and Ms Carr will be represented by Michael Hubbard QC.
The trial judge is Mr Justice Moses and the case is expected to last three or four months.