Sitting on a red velvet chair in the middle of a majestic, oak-panelled hall in East Grinstead, I have rarely felt more fearful for my sanity. On the wall in front of me, a creepy, larger-than-life-sized portrait of an old man seems to be staring straight at me. In front of the portrait, Laura, a middle-aged woman wearing a high-necked blouse and ostentatious gold cross, stands behind a lectern reading aloud from a huge leather-bound tome.
None of the worshippers take their eyes off Laura as they repeat her words back to her. Phrases such as: "All men have inalienable rights to think freely, to talk freely, to write freely their own opinions and to counter or utter or write upon the opinions of others" are made ridiculous by the followers repeating them in a monotonous drone.
I am at Saint Hill Manor in East Grinstead, West Sussex - the UK's Church of Scientology headquarters. In the few hours I spend at Saint Hill I realise this exercise is anything but innocuous, and might go some way to explaining why Katie Holmes, the one-time girl next door of American television, has been enveloped into the cult championed by the father of her unborn baby, Tom Cruise.
After much talk of her staying silent during the birth, in accordance with Scientology's beliefs that babies born to the sounds of their mothers screaming are more likely to encounter emotional problems in later life, Cruise announced in an interview with ABC's Diane Sawyer that Holmes is no longer a Catholic. Asked whether their baby would be baptised a Catholic, he said: "You can be Catholic and a Scientologist. You can be Jewish and a Scientologist. But we're just Scientologists."
Cruise and Holmes are not alone. Kelly Preston, John Travolta, Kirstie Alley, Isaac Hayes, and Priscilla and Lisa-Marie Presley are also members of the sect, created in 1954 by the pulp science-fiction writer L Ron Hubbard. It is his portrait that hangs in Saint Hill. Intrigued by a cult that believes humans are the descendants of aliens, I have come to Saint Hill to find out what really goes on in the "church".
Very few journalists have infiltrated this bizarre "religion", although it has attracted at least eight million followers and is estimated to make £250m a year from its members.
Posing as an interested disciple, I first call into the Scientology Centre on London's Tottenham Court Road where I fill out an Oxford Capacity Analysis Test, designed to measure emotional state in order to highlight areas that Scientology can improve. Although the test is free, I am encouraged to purchase a copy of Hubbard's Dianetics (for £6.99) and to contact them when I finish reading it.
My results apparently prove that I am depressed, nervous, critical, anxious and unable to communicate. I am told that I am in dire need of spiritual enlightenment and that only Scientology can help me.
I telephone the Church of Scientology's headquarters at Saint Hill, claiming that I am concerned by my test results. I am invited to attend a "church" service, a "group processing session", and to have a guided tour by a "recruitment expert" of the building and grounds at Saint Hill, known to those inside as "The Castle".
Two days later, I am standing on the manicured lawns of the beautiful Jacobean building that is home to Scientology's version of the civil service - the Sea Organisation. My guide for the day, Ron, appears. He tells me has been a member for seven years and sold his home in Norwich six years ago "to be closer to the Sea Organisation". He works at Saint Hill every evening and weekend. He has a day job as an electrician and seems surprised when I ask him if he has time off. "Why would I want to do that?" asks the 33-year-old. "I love it here."
As Ron guides me around the vast building, I notice several recruits going about their daily tasks. Weeding, sweeping, cooking and cleaning, the tasks are performed silently - free of charge - by followers who cannot afford to pay the exorbitant costs of the study courses that would bump them up Scientology's hierarchichal system.
Part of my tour takes in converted outbuildings that comprise a sauna, showers and a gym area. Three teenage boys and a girl wearing swimsuits are sitting eating a spartan meal of rice and beans. "These people are undergoing a period of purging," Ron tells me. After taking a variety of vitamins and minerals designed to cure addiction, they spend the day alternately sweating in the sauna and running full tilt on the machines. When I ask what the purpose of the exercise is, Ron is unable to tell me whether these youngsters are addicted to alcohol or drugs - they're just "addicts".
None of them look up when I say hello. They do not even look at each other. Ron doesn't appear to see anything strange in their behaviour. "People come here to be cured of things - physical addictions, mental distress and spiritual travail," he says. "They can only really begin to work on their Scientology when they are are cleared of all the poisons in their bodies - and this is what the purging is for." He tells me that if I am serious about wanting to join up, I will need to do this too.
I ask if Scientology is a drug rehabilitation programme or a religion and he can't give me a straight answer: "It's different things for different people, you know," he says. I don't. "Well, people have all different kinds of problems and Scientology can help anyone through anything. It makes you a better person."
Quite what Scientology does for the individual has been a matter of debate since Hubbard set it up in 1954. Tellingly, four years earlier, he had announced at an authors' convention: "Writing for a penny a word is ridiculous. If a man really wants to make a million dollars he should start his own religion."
Aged 42, he declared that humans are descendants of an exiled race from outer space called Thetans and that we are nothing more than temporary vessels for the immortal souls of Thetans. Only by exorcising painful memories of our past incarnations can we achieve our full potential and reach spiritual salvation. Scientologists believe that life is a relentless struggle towards the total erasing of painful mental images - called "engrams" - that accumulate through successive incarnations.
The cult has always had its detractors. In 1984, Mr Justice Latey, giving judgement in open court after a private hearing, branded the scientologists "corrupt, sinister and immoral". In 1991, Cynthia Kisser, former executive director of the American Cult Awareness Network, proclaimed that "Scientology is quite likely the most ruthless, the most litigious and the most lucrative cult the country has ever seen." In 1994, the Californian Court of Appeal accepted that the techniques of scientology constituted brainwashing. In Britain, the Charity Commission denied Scientology religious status on the basis that it did not benefit the public in any way.
As I'm led inside another room by Ron, I see at least 100 people - most of them elderly - poring over huge leather-bound books. It reminds me of one of the large reading room in the British Library - but these people are not browsing for free. Although Ron will not give me an exact figure, he says that recruits pay "thousands" to study Scientology.
Elsewhere, there are hundreds of machines stacked up in readiness for a possible sales event that afternoon. Called E-meters (short for electropsychometer) they look like two tin cans attached by thin wires to a navy blue control panel. By gripping the cans in both hands, the specially designed machine will supposedly help senior Scientologists locate areas of spiritual distress in your soul. Although the Scientologists' own prayer book states they can only be used by Scientology ministers, I - a definite non-minister - am offered the chance to purchase one, a snip at £3,000.
I ask Ron whether I'm likely to bump into any famous names. He shakes his head. "Celebrities rarely attend Saint Hill, except on special occasions," he says. "There is a dedicated 'celebrity centre' in London's Bayswater." Apparently, celebrities have "special needs", although he won't expand on this. Somehow, I can't envisage Cruise or Travolta sleeping in a barracks in East Grinstead.
At the end of the four hours, I am keen to leave. Ron tries to get me to make an appointment to see someone for "dianetics counselling" as soon as possible. He phones me that evening - and for the next three days. A female recruit also leaves me messages - none of which I return.
The cult has attempted to intimidate news organisations who expose it. Last year, it threatened court action against Google, which had to remove websites that criticised the group. After a day witnessing what goes on on the inside, I realise it's little wonder the "church" needs to resort to such tactics.