Two schoolgirls were attacked during a "terrible ordeal of rape, humiliation and degradation" after being lured to a park by a gang of boys, a court heard.
The girls were targeted by the three boys, aged 13 and 14, after getting on a bus in south-east London in November 2006, Inner London Crown Court heard.
The boys, who cannot be named for legal reasons, deny all the charges against them including six counts of rape.
The trial, expected to last up to two weeks, was adjourned until Tuesday.
Indignity and degradation
Mr Lucas, prosecuting, said: "These boys bullied and committed terrible sexual violence against these two young girls and subjected them to indignity and degradation."
The boys got on the bus several stops after the girls and began spray painting graffiti on the windows and ceiling before approaching their victims, jurors heard.
Mr Lucas said the conversation soon took on a more suggestive tone.
The girls got off the bus early but they did not know the area and agreed to let the boys show them to the next stop.
Instead, the gang led the pair into a park where they carried out their 40-minute attack.
Mr Lucas said one was first forced to perform a sex act on one of the 14-year-olds, before being made to partially strip. He said she was then raped.
The barrister said before she had time to recover from her ordeal she was forced to have oral sex with the other two.
He told the court that in the meantime the second girl had also been ordered to perform a similar sex act on one of the boys.
Mr Lucas continued: "Both girls thought that during the course of the sexual assault they remembered one of the boys holding a phone up and it bleeping as if recording what was going on."
After their ordeal, the girls ran to a nearby house and police were called.
The trial continues.