They did that so well, starting out like a corny live daytime TV-ish thing and slowly ratcheting up the weirdness, taking full advantage of the phase everyone would go through where they were uncertain if it was really live or a hoax.
I doubt you'd get any impression of what it was like then by watching it now, because all the social context is gone, but as a kid at the time it was really scary.
Is that intended as a correction? If so, I said "daytime TV -ish". I meant the initial vibe was similar to the lighthearted fare the BBC and other channels put out during the day at that time, albeit with jokey "spooky" trappings, despite its post-watershed airing. I know it was on late, I watched it "live".
The fact that they were investigating night time paranormal activity even gave them an excuse for airing such seemingly kid-friendly stuff so late in the evening. A lot of parents let their kids stay up for it, including mine.
I doubt you'd get any impression of what it was like then by watching it now, because all the social context is gone, but as a kid at the time it was really scary.