Pope Benedict apologized to victims of sexual abuse on Saturday, saying pedophile priests had brought "shame and humiliation" on him and the entire Roman Catholic Church.
Pope Benedict began his third day in London holding separate meetings with Prime Minister David Cameron, deputy Prime Minister Nick Clegg and the leader of the opposition Harriet Harman.
He then celebrated mass in Westminster Cathedral, the mother church for Roman Catholics in England and Wales. Fifteen-hundred people took part in the service inside the church. Over 2,000 young people followed the mass on giant screens outside the cathedral.
The pope wore bright red vestments for this service. For the second time during this visit to Britain he turned his thought to the victims of clerical sex abuse.
"Above all, I express my deep sorrow to the innocent victims of these unspeakable crimes," he said.
The pope acknowledged the shame and humiliation that everyone has suffered. He expressed hope that this humiliation would contribute to the healing of the victims, the purification of the church and renew an age-old commitment to educating the young.
"I express my gratitude for the efforts being made to address this problem responsibly, and I ask all of you to show your concern for the victims and solidarity with your priests," he said.
As he traveled to Britain, Benedict acknowledged to reporters that the church had failed to act quickly or decisively enough to stop the abuse and prevent it from recurring. There is speculation that the pope could meet British victims of sexual abuse but the Vatican has yet to confirm this.
A big march through London is taking place Saturday, organized by opponents of Pope Benedict's visit to Britain. Demonstrators say the church must do more to remove those guilty of sexual abuse on children. They are calling for the pope to hand over to the authorities all information on abusive priests. They are also protesting the church's positions on homosexuality and on using condoms to fight AIDS.
The pope flies to Birmingham in central England Sunday, the final day of his visit to Britain, where he will celebrate a beatification ceremony of 19th century cardinal, John Henry Newman.