Graeme Swann
From Tardis Wiki, the free Doctor Who reference
Graeme Swann was a cricketer who, in an altered 2008, was, according to The Times, "100 not out". The Fifth Doctor used this as evidence to Nyssa that the world had been changed — that it was a little bit better and more "perfect". (AUDIO: A Perfect World)
Behind the scenes
The joke here was quite topical, and would have made sense until 2008. For several years before December 2013, Swann had struggled in cricket, so the point of the joke is that a perpetually inconsistent cricketer finally found his form. In real life, however, Swann actually did find his form starting with a test match against India in December 2008, and has been one of England's better players in the early 2010s.
