Christians met in front of Parliament on Saturday to pray for the nation and launch this year's Pentecost Festival, also known as the Biggest Birthday Party Ever.
Pentecost is when the Apostles received the Holy Spirit, marking the birth of the church.
The outdoor prayer gathering was intended as a "creative and visual expression" of the Christian faith.
It was opened by Andy Frost, director of Share Jesus International, the organisation behind Pentecost Festival.
He spoke of the need for the church to have vision and unity.
"Let us give thanks for this great day and a chance for us all to gather and pray for the Church, and those working in the Church," he added.
Celia Brown, from advocacy group CARE, spoke of the need to care for the vulnerable in society, especially children.
She also stressed the importance of strengthening families and communities.
"Let us pray for all our children and those who are confronted with graphic images and pornography," she said.
Prayers were said for the Queen, politicians, and Christians working in government, as well as for wisdom for local authorities and key influencers in society, including those working in the media and business.
Prayers were also said for young people and those in the position to be role models for them. Youths caught up in gangs were a particular prayer point.
Emma Worrall, of Open Doors shared about suffering to Christians and others being caused by the crisis in Syria and her hopes for an end to the civil war there.
The closing praying was said by the Bishop of London, Dr Richard Chartres.
He said: "The Holy Spirit continually challenges us and surprises us by breaking out of the familiar, leading us into new and unexpected places". Across London there'll be nearly one hundred events involving many thousands of people. Churches are the people and we're bringing the churches out of their buildings and onto the streets.
The evening was then followed by the 'Release of the Spirit at Pentecost' concert at the Methodist Central Hall.
The hall was packed for the concert, which featured performances by Rend Collective and Noel Robinson, Doxa Deo and Guvna B.
Talks, concerts and other events will be taking place throughout the week as part of Pentecost Festival.