This year's Greenbelt Festival is taking place under the banner of 'Wit & Wisdom' and the eclectic line-up includes TV personality Russell Brand, singer-songwriter Frank Turner and controversial Lutheran pastor Nadia Bolz-Weber. 

The Christian festival is a staple on the annual events calendar for many in the church, even those who don't necessarily agree with the theological or political leanings of the speakers. 

It is being held this year from 23 to 26 August at Boughton House, Northants, and continues its tradition of bringing together worship, music, social justice and the arts. 

Brand is one of the headlining acts.  In the past, the comedian, TV presenter and actor has been just as open about his struggle with drugs and sex addiction as he has been about his spiritual searchings and beliefs about God.

While his inclinations may be more 'New Age' than Christian, he has in the past shown a genuine and respectful interest in the religion, as revealed by an intriguing conversation with Oxford professor and apologist Alister McGrath. 

In their discussion, titled 'Is there any point in God?', Brand said he liked the idea of Christ's call to "die to self" and being "decentred by something bigger", although he was also sympathetic to the atheist worldview and admired the achievements of science in solving some of the big problems of mankind. 

Never one to stick with convention, Greenbelt's diverse line-up this year also includes Nadia Bolz-Weber, a pastor and New York Times bestselling author who has angered Christians with her liberal views on issues like the adult industry, abortion and sexual purity. 

Last month, she presented the sculpture of a vulva made out of old purity rings to pro-abortion second-wave feminist Gloria Steinem. 

In the past, she has defended "ethically sourced [adult content]" and this year, stoked the ire of the evangelical church further with her new book 'Shameless' in which she argues that many of the church's ideas about sexual purity are antiquated. 

The full line-up is below: