They call themselves the most hated family in the US and they picket funerals of soldiers killed in Iraq. So what did Louis Theroux make of the Phelpses after three weeks?
In any country, let alone one as patriotic as the US, few actions are as provocative as protesting at a soldier's funeral.
The Phelps family pickets mourners across the country, to mark what it describes as God's revenge on the US for tolerating homosexuality.
Their actions are in the name of the Westboro Baptist Church, which numbers 71 and is headed by "Gramps", preacher Fred Phelps. The church, which is based in Topeka, Kansas, mostly comprises his extended family.
Louis Theroux, himself no stranger to people with unconventional views, says the Phelpses are the most extreme people he has ever met. But in the following interview, he reveals how three weeks with them left him perplexed by their motivation.