Until the Fourth Doctor and the renegade Time Lord known as the Master rediscovered it in The Deadly Assassin some even believing it to be mythical or no longer in existence .
The Deadly Assassin is the Time Lords had forgotten its location .
Until the Fourth Doctor and the renegade Time Lord known as the Master rediscovered it in The Deadly Assassin , the Time Lords had forgotten its location , some even believing it to be mythical or no longer in existence .