I watched a programme on the 1977 poltergeist hauntings in Enfield; it was on the Discovery channel and was very interesting.
I watched it incredibly closely and, if you do get to see it, then watch the parts where they're filming Janet Hodgeson where the 'voice' talks - you can see her lips move. Not very much and I can understand why those there at the time might have missed it, but you can clearly see her lips move in time to the words and, later in the programme, you can see her throat move as if she's talking deeply in her throat and trying not to move her lips.
Even the Daily Mirror photographer who'd previously been a believer, said that the voice just wasn't credible and he began to feel it was all being done because by now the investigators and others who were there were expecting it.
Certainly the girl who was the centre of it hardly seemed very frightened when interviewed; her sister seemed more subdued by it all whereas she was grinning and giggling.
One of those things that make you go hmmm........
I personally thought, by the end of the programme, that whilst there might have been a little something in the beginning the rest was fake. Just MO though.