What the activists said to the bishops

It was, in the Prime Minister's words, "one of the greatest public demonstrations of faith that this country has ever seen". And certainly, it was a rare sight: almost 670 bishops – a sea of purple – moving slowly and silently through the streets of central London.

In front of them on this "walk of witness and solidarity" was their leader, the Archbishop of Canterbury, Rowan Williams, and a poignant banner appealing for those in power to "Keep the Promise [and] Halve World Poverty" by 2015, as pledged by the United Nations.

They had come in coaches from Canterbury, host to the once-a-decade Lambeth Conference where the bishops are spread across a sprawling university campus riddled with journalists looking for Anglican splits over homosexuality and gender.

But – flanked by 1,500 other faith leaders, diplomats, politicians and charity heads – there was no mistaking their unity yesterday as they moved as one body in the name of justice and peace for the higher causes of their mission. Among those joining them were Cardinal Cormac Murphy-O'Connor, the Roman Catholic Archbishop of Westminster; Rabbi Sir Jonathan Sacks, the Chief Rabbi; Sir Iqbal Sacranie; Dr Indarjit Singh; and other senior representatives of Muslim and Sikh organisations.

Inside Lambeth Palace, Dr Williams's home and the scene of several stormy controversies in recent months, the bishops listened to a clearly moved Gordon Brown as he showed that he had heard their message. "A hundred years is too long to wait for justice and that is why we must act now," Mr Brown said. "You have sent a symbol, a very clear message with rising force that poverty can be eradicated, poverty must be eradicated and if we all work together for change poverty will be eradicated."

Earlier, the Archbishop had presented Mr Brown with a letter – the event's "manifesto" – warning that most of the UN's Millennium Development Goals agreed in 2000 are at risk of never being achieved.

Dr Williams also added a new challenge, urging world leaders to invest in and strengthen their partnership with the church worldwide, so that its extensive delivery network for education and healthcare, alongside other faiths, is fully used in the eradication of extreme poverty.