The Doctor's name - and the question that must never be asked. Are they the same thing? A lot of people seem to think that the oldest question, the one hiding in plain sight, is "Doctor Who?". Obviously it can't be as simple as this, as several characters have asked that question throughout the entire history of the programme - from the Doctor himself, when Ian calls him Dr. Foreman in An Unearthly Child, through Dorium Maldovar to the Dalek Parliament. If the Doctor's identity is connected to the oldest question - that must mean we are in the realms of what was referred to as the Cartmel Masterplan. As the programme was coming to an end in 1989, some of the writers posited theories that the Doctor was no mere Time Lord but a member of a triumvirate (along with Rassilon and Omega) from the dawn of the Time Lords. How else might his name be the oldest question?
Personally, I think the question has nothing to do with his name. I can't see Moffat naming the Doctor on his watch. Every time a production team has given away a bit more knowledge about the Doctor and his background, I feel the character has been diminished rather than enriched.
Doctor Who is the name of the TV programme. There has never been a question mark though many take it to refer to a mystery regarding his identity. Doctor Who is also how each actor has been credited up to the point David Tennant took over. The general public always refer to the character as Doctor Who. Episode 5 of The Chase is called "The Death of Doctor Who". However, there is no point ever in any episode where he has used this name himself. He is always simply "the Doctor".
The War Machines seems to throw a spanner in the works when WOTAN specifically calls him "Doctor Who". In my last post (on mad computers) I put forward my proposal that the machine has a telepathic ability (hence it knowing what TARDIS stands for). Remember it can hypnotise and take people over without them coming into physical contact with it. It has read a gap in Dodo's knowledge and substituted a question - as it can't find the name. It's as good a theory as any other.
When we get to the early Troughton years we have the Doctor adopting the alias Dr. Von Wer in The Highlanders (German for "who"), and in The Underwater Menace he signs a note to Professor Zaroff "Dr. W".
Both stories are made by the same production team who may simply have thought Who was his name. It may equally be a joke on the Doctor's part - as people keep asking him who he is.
Jump forward to 1988's Remembrance of the Daleks and we get a clear view of the Doctor's calling card. His name appears to be a mathematical hieroglyph. Seems a bit complicated for "Who" to me. The use of a question mark might imply the Doctor finds it quite funny that no-one knows who he is - not necessarily that he is called Who.
River Song knows what his real name is, as she tells it to him in the Library in order to gain his trust. Watch that scene carefully. If his name is just "Who" then she takes a heck of a long time to whisper one syllable. Of course he may have an incredibly long first name - but it is the surname which defines us, says who we are and where we came from, so it's not "Doctor Something Who" for me...