Blondie is the prior incarnation of Acne Doctor. After losing his Tardis in a strip poker game he was forced to travel through time with his future self, however he was never allowed to leave to Tardis or touch the controls, effectively being cucked by his own time machine.
Blondie when the way of the Dodo once the actor the actor realized just how autistic the whole thing was, leading to his final scenes not actually showing his face at all, what a fucking joke.
BUT WAIT! Edit
Warning: Spoilers and/or plot/ending details follow. As if you give a shit.
In Series 2 Episode 5, Into the Mind, an amnesiac Acne Doctor was plunged into a journey of mental discovery. In the middle of winding up on some beach somewhere in his memories, he suddenly ran into a familiar-looking blonde lad who managed to restore his true self-knowledge.
BUT WAIT, AGAIN! Edit
Still spoilers but even moreso this time.
In the first and probably only GOAT twist of the entire series, Blondie made a startling appearance in Series 3 Episode 3, Power of the Puppeteer, and it was revealed that he was not what he seemed.