For almost half a century, the BBC produced documentary series Doctor Who has been beamed into our portable picture palaces and has well and truly etched its way into our collective consciousness. I think we can take it pretty well much as fact that the BBC has a network of news gatherers throughout our sector of the Milky Way and that the Controllers of the BBC have signed some sort of non-disclosure agreement with the Sub-Sector Government to ensure that Earth doesn't get technology before its time (insofar as time itself is linear and not a wibbly-wobbly-timey-wimey ball of stuff as hypermathematics now knows it to be).
We can therefore assume that the person on Doctor Who is only playing at being The Doctor and that the actual Doctor is somewhere on Earth, in relative obscurity. If this is the case, then who amongst the now seven and a bit billion of us is the one person who isn't human? Who of all of us is a ring in?
We can ascertain that The Doctor is likely to be a tinkerer; someone either engaged in a technical or semi-technical field. We also know that because the TARDIS is an old and unreliable "ship", that its owner would have to be meticulous in its maintenance.
The Doctor is often shown on telly as being frequently annoyed at other people either breaking things but he himself is not above hitting things with hammers or pressing buttons of completely unknown function.
It can be pretty much taken as fact that flying the TARDIS requires skill but that because it is a time travel device, its owner would not be all that bothered about arriving late or on time because they could just ad easily change the point in the time stream that they wanted to appear in. Our suspect would therefore be likely to be accused of being tardy and have no conscience in this regard, they may even wear such a tag as an epithet.
The TARDIS itself has had many changes of interface over the years and all of them appear to be outdated for the relative time that they're in. The Doctor himself has stated amongst other things that Stetson hats, fezes, scarves, ruffs and bow ties are "cool"; so clearly The Doctor is someone who has no fashion sense whatsoever and given the opportunity would probably own a range of downright hideous looking shirts.
Operating the central console of the TARDIS is akin to playing a very complicated instrument. The Doctor doesn't dance but we can assume that after travelling throughout time and space that he has probably picked up a good ear for music. Since the invention of the piano circa 1698, it has become the instrument of default for the majority of composers because of its tonal range and because the word pianoforte means "soft loud", it also is able to carry a lot of the functions of the various voices of a full orchestra.
The documentary series suggests that The Doctor is hiding as someone British because Gallifrey's accents mimic those of the UK. Even The Doctor himself when asked about his accent said that "lots of planets have a north" which I can only assume to mean that Gallifrey through some freaky coincidence (that wobbly-wobbly-timey-wimey thing again) has a set of accents similar to the UK; hence the reason why he'd want to hide there.
So then, we're looking for a fashion illiterate, piano playing, tinkerer who is accused of being late or slow and appears to be British. The only logical candidate in the world then is James May. This also fits together the facts that the BBC doesn't generally shoot episodes of TopGear whilst they're filming Doctor Who for "budgetary reasons".
The jig is up James, you've been ousted... James May is Doctor Who. Matt Smith is just an actor.
No one would knowingly wear shirts that hideous unless they were The Doctor would they?
All the facts fit together. His telly show James May's Man Lab is all about getting out and making things and doing things. No-one else would logically conceive that tinkering with an unexploded German 500 pound bomb was a good idea and there can't be any other reason why he likes to hang about with a person of the species Cricetinae Sapiens (Hamster people) and a companion who likes to use hammers for basic maintenance. He is an incredibly talented piano player and has presented telly programs about all manner of science, technology, toys, pastimes, culture and the decline of mankind. It also makes sense that he'd make a documentary about the moon landings and go to the edge of space in a U2 spy plane, considering that he'd been there before.
I'd also go as far to suggest that in 1963 during the Dalek Invasion of Earth, that he was able to tinker events such that Kennedy was shot just at the right time so that no-one would even notice the seriousness of the situation.
Of course it makes sense that James May is The Doctor. That is the most logical conclusion.