IN THE pouring rain at six p.m. on Tuesday night, in the heart of London, workmen in hard hats, elevated eight metres above the ground, were not quite finished. Nevertheless, just the top of the tower of St James's, Piccadilly, remained visible, the rest of Sir Christopher Wren's church obscured by a thick grey wall, topped with barbed wire. Floodlights powered by a generator struggled in the wind and rain.

Despite the conditions, more than a hundred people were present to witness the unveiling of Wall, a replica of the separation barrier constructed in Bethlehem. The installation is part of a 12-day festival at the church - Bethlehem Unwrapped - designed to celebrate Bethlehem through art, music, food and debate.

Members of the public are invited to write prayers and messages of hope on the wall. Inside the church is an exhibition of art by children living in Bethlehem, entitled All They Paint is the Wall. On Tuesday night, their pictures were projected on to Wall, bearing witness to the collection's title, a quote from one of the children's teachers at Dar Al-Kalima Lutheran school.

The festival's curator, Justin Butcher, who created Wall, described it as a response to the Kairos Palestine document issued by the churches of the Holy Land in 2009 (News, 11 December 2009). This document states that "the Israeli occupation of Palestinian land is a sin against God and humanity because it deprives the Palestinians of their basic human rights, bestowed by God." It calls on the international community to "stand by the Palestinian people who have faced oppression, displacement, suffering and clear apartheid for more than six decades". The statement is critical of the separation barrier.

Israel began building a barrier in and around the West Bank in 2002, with the stated aim of preventing attacks by Palestinians inside Israel. It is planned to cover 712 km (442 miles) and is currently 62 per cent complete. The UN Office for the Coordination of Humanitarian Affairs (UNOCHA) reported this year that 85 per cent of the route is inside the West Bank. Around 11,000 Palestinians living in 32 communities located behind the barrier depend on the granting of permits or special arrangements to live in their own homes. UNOCHA warned this year that the completion of the barrier in Western Bethlehem would "sever the urban area from its agricultural lands" and reduce the access of more than 23,000 residents to Bethlehem City, their chief centre for health, education, and trade. In 2004, the International Court of Justice issued an advisory opinion which stated that the construction of the wall inside the West Bank violated Israel's obligations under international law. The court called on Israel to cease construction of the Barrier, dismantle the sections already completed, and repeal all legislative measures related to that the Barrier.

On Tuesday, the Rector of St James's, the Revd Lucy Winkett, said that the Church had been asked many times, "But why are you doing this? Twenty of us went to visit Israel and the Palestinian territories in October and one of the lasting memories of our time there was this wall. It looks exactly like this. For most people possibly, Bethlehem is not a real place. It is a mythical place. . . We at St James's are glad and proud to be supporting the town of Bethlehem this Christmas."

She suggested that it was "unhelpful to be pro one side or the other. We are inviting members of the public to come and write on this wall messages of hope and peace for the people of Bethlehem. There will be no censorship unless it is divisive."

In a video message recorded in Bethlehem and projected on to the wall, Sami Awad, director of Holy Land Trust, said: "It is not enough just to know what is happening in Bethlehem. . . The people who live in Bethlehem under occupation, surrounded by walls and fences . . . the message to you is 'Come and see, come and see what life is like in Bethlehem, and be witness to the injustice that is happening in this city.'"

Jeff Halper, founder and director of the Israeli Committee Against House Demolitions, said: "This is a very courageous thing for a church to do, to speak up like this."

He described the wall constructed by Israel as a "deadly barrier that people cannot pass". It was not a security measure but "built in a way that allows the settlements to grow. It defines the cantons in which Palestinians will be confined. It does not separate Israelis from Palestinians, it separates Palestinians from Palestinians."

He said: "If we are speaking about sides, I think there are sides. It does not break down into Israelis and Palestinians, but it breaks down into people that think human rights are the way we have to live our lives and those that believe that violence and division and sectarianism is the way. I think we are on the side of human rights."

The festival will feature an evening of slam poetry on Sunday, stand-up comedy on Monday, and a Christmas supper served by the chefs Yotam Ottolenghi and Sami Tamimi on 3 January. At the end of 12 days, on Sunday 5 January, the violinist Nigel Kennedy will perform his original composition, The Bridge, and Wall will be "transformed into a symbol of peace".

All profits from the festival will be donated to the Future Peacemakers Appeal, Holy Land Trust, Bethlehem.