A committed Scientologist, Mr Travolta accuses Mr Jackson and Alan Hayling, the programme's commissioning editor, of being prepared to slander him and all the members of the church. He claims they seem intent on inciting hatred of the sect, as had been happening in Germany, where the authorities are suppressing its activities. The actor mysteriously asks whether the persecution of Scientologists will stop only when someone like himself becomes a victim.
The star of Saturday Fight Fever and Pulp Fiction implores the television executives to let true friends of Mr Hubbard, who died in 1986, to be interviewed for the Secret Lives edition scheduled for 19 November. The programme, which has been completed, pulls apart the Hubbard legend, accusing him of being a fraud. Several of those interviewed were among his inner circle.
The sect has reacted with fury to the programme and has fought hard to have it cancelled. Channel 4 has been bombarded with letters and phone calls from members around the world. Senior sect officials have twice had to be asked to leave the channel's London headquarters after turning up and demanding to meet Mr Jackson.
The crew from the independent company making the programme were followed across America and have been visited by private detectives acting for the church at their homes in England. They even visited the stables where the director, Jill Robinson, keeps her horse. She found the visit threatening. "I was not there at the time and I cannot see what they were trying to do except make it clear to me that they knew where I kept my horse," she said. "I regard it as intimidating."
In the past few days, the campaign against the programme has taken on a surreal aspect, with a camera crew from "Freedom Films", thought to be a Scientology production unit, arriving unannounced and filming the programme makers at their homes.
Mr Hayling said there was no question of the programme being changed or stopped. It was based on factual material and interviews with people who had known Mr Hubbard well. When first asked to co-operate, the church had not responded. Only later did it offer access, but on condition that it had editorial control. Mr Hayling described as "deplorable" the visiting of members of the film crew at their homes.
The Church of Scientology said it was "absolutely untrue" that it had initially refused to co-operate. The private detectives were justified, a spokesman said, because the organisation was making its own inquiry into whether those involved in the making of the programme were linked to people in America who had been trying to extort cash from it. Focus, Page 20