LONDON  On a day when he faced by far the largest protests of his four-day state visit to Britain, Pope Benedict XVI used an address at a Mass in Westminster Cathedral on Saturday to reiterate his “deep sorrow” for the “unspeakable crimes” of child abuse within the Roman Catholic Church.

His remarks followed other recent comments in which he has struck an increasingly remorseful tone about the abuse scandal. But they took on added weight for the fact that they were made before 2,000 worshipers in the cathedral that is the seat of Catholicism in England, and ahead of a protest march on a scale rare in the recent history of the papacy.

“Here, too, I think of the immense suffering caused by the abuse of children, especially within the church and by her ministers,” Benedict said at the Mass, which was attended by hundreds of clergy members and prominent Catholics, including former Prime Minister Tony Blair, a convert to Catholicism.

“Above all, I express my deep sorrow to the innocent victims of these unspeakable crimes, along with my hope that the power of Christ’s grace, his sacrifice of reconciliation, will bring deep healing and peace to their lives,” he said. “I also acknowledge, with you, the shame and humiliation which all of us have suffered because of these sins.”