Christel Doctor of the Week - The Guardians of Time

We first saw the white guardian of time at the end of Christel Doctor Who Series 1. He warned the Doctor that he being put through a test, which it was implied, the guardians were controlling. The White Guardian also hinted at the involvement of other guardians but they were not seen. Perhaps the most important was the revelation that the doctor will meet the guardains twice more and when he meets them for the final time he shall "know himself". hmmm...intriguing...