Benefitting from the healing undergone by his predecessor, the Tenth Doctor possessed an outgoing, lively and genial demeanour that hid his underlying guilt, but it was still present and would appear if the Doctor was overwhelmed.
For most of his life, the Doctor was able to successfully project a convivial and even frivolous front. However, when he had to engage in conflict, the Doctor’s energies would shift to reveal a fiercely protective man who resolutely guarded what he held dear, and who could be viciously unforgiving to the forces that dared menace them.
Tenth Doctor's Quotes Buy Tenth Doctor Collectables TARDIS Wiki