After a somewhat dynamic and brightly-flaring sixth Doctor, it perhaps seems strange that his next regeneration would be triggered apparently by his falling to the floor of the TARDIS during an attack by the Rani, another renegade Time Lord. He was promptly kidnapped, drugged and mentally confused by the Rani and it wasn't for some time that the Doctor realised who he really was.
Not surprisingly, this treatment resulted in an initial period of uncertainty and instability, but the Doctor's emerging character featured traits from all his predecessors: wisdom, unpredictable clownishness, a love of gadgets, mystery, the ability to be underestimated and a volatile temper.
This Doctor was also seen to have hidden depths and undercurrents. There was a new sense of mystery and intrigue over his origins: he hinted at being more than just a Time Lord, and a witch from the 17th Century seemed to know many 'secrets' about him, all of which remained untold. If the Doctor was a Time Lord, then his role in the history of that race was in the process of being reassessed.
The seventh Doctor could be dark and manipulative, secretive and angst-ridden, keeping his cards very close to his chest and only allowing others to glimpse a fraction of his true motives and aims. He could also be unpredictable and flippant, enjoying teasing others with his apparent lack of concern when, inside, he was plotting and scheming a way to save everyone. He could happily delay the Gods of Ragnarok with an endless presentation of magical tricks and feats of dexterity and could even use some form of psychic power to incapacitate those who threatened to stand in his way.
Alongside all these traits, he also took on the role of teacher to his companion Ace, often forcing her to confront aspects of her past and personality that she would rather remain buried. Ace flowered under the Doctor's tutelage, and they eventually grew to respect and trust each other. 1998 David J Howe