Ecclesiology will be under the spotlight in tonight's Everyman programme which uncovers the secrets of the Exclusive Brethren.
To be screened on BBC2 at 11.30pm it will examine the denomination which, since it's foundation in the 1830s has kept itself apart from society.
Members of the Christian sect - which claims as many as 15,000 members and are present in around 100 towns in Britain - keep themselves separate from the world which they consider to be evil and strenuously guard their privacy.
They Brethren aim to provide strong family units, a firm moral framework and enforce strict rules for separation from the world.
Members cannot eat with non-members, be friends with them or join any professional organisations with them. They can only marry each other and children grow up to fear the outside world.
In the past, they have used the law to prevent any examination by the media - they consider radio waves 'pipelines of filth' and have banned all apparatus using them.
But there are signs that things may be changing. As a result of the issues highlighted in tonight's programme, the Brethren are apparently modifying their practices and apologising for their 'unChristian behaviour'.
With a new leader in place, the future of the Brethren is looking far from certain.