User:SOTO/Forum Archive/The Reference Desk/@comment-90.202.235.30-20150819012613/@comment-1432718-20150819020603
From Tardis Wiki, the free Doctor Who reference
Actually, we had a similar question asked a few months ago at Thread:165490. We have no way of knowing any more than was revealed in the story, but you might be interested in some of the comments posted on that old thread.
