The Time Lords are at the very heart of Doctor Who mythology - the civilisation that conquered the fourth dimension, took a strict vow of non-interference in the affairs of the universe, broke it on the sly, went to apocalyptic war with the Daleks and drove one of their kind to nick a faulty TARDIS and go on the run, spreading justice and jelly babies across space and time.
Where would be without them? Watching ITV on a Saturday night, that's where.
Now a new book unlocks the secrets of this ancient, legendary race. A Brief History of Time Lords by Steve Tribe is packed with crucial facts on the Gallifreyans and illustrated with original full-colour art from concept artist Richard Williams.
It's out now in hardback from BBC Books. We have six copies up for grabs. To be in with a chance of winning, simply match your mind against this question: