Actress Brooke Kinsella played her most difficult role when she helped police build the case up against her brother's killers.
She fought back tears to appeal for youngsters to come forward to tell officers about the terrible stabbing which ended the promising life of Ben.
She urged them to "make a stand to help the police" after it was revealed that frightened youngsters were holding back.
But after her appeal, and with the knowledge that three suspects were in custody, the teenagers made statements to police.
The day before her appeal, Brooke had led 400 people on a local march to protest against youngsters being killed by knife crime.
She said: "Recently, there has been a lot of publicity over knife crime, especially involving young people.
"We marched in Islington to show community opposition to it. But we all really need to make a stand and to help the police."
Brooke, 25, who played Kelly Taylor in EastEnders, thanked members of the public for providing "significant information".
She described her brother as "entirely innocent" and said: "All we've got left of Ben now is memories and that's not very fair, in my eyes.
"My last memory of him is I bought him some McDonald's. I have got too many memories of Ben that I can't possibly ever tell you."
Brooke, her mother Deborah, 46, father George, 48, and her sisters, attended the six week Old Bailey trial.
They sat only feet away from the accused and were supported by a group of friends and relatives in the public gallery.