Ghosthunters UK was a TV series about ghosts. We've discussed it before but now it's now on YouTube woohoo!
The chap who saw the Roman soldiers in the cellar was called Harry. I think he died a few years ago. His account is in the first episode.
Harry's account was debunked in the pages of the FT a few issues ago. We have a thread on it. Basically, the story came to light decades after it was supposed to have happened, and may have been embellished or just plain made up.