The mystery of the Doctor’s name is one of the most enduring puzzles in Doctor Who, with suggestions for the Time Lord’s secret moniker including Theta Sigma, δ³Σx² and, er, Basil.

But despite these clues, the Doctor’s name has remained a secret for over 50 years – and one new fan theory might reveal exactly why it’s been so tricky to find out.

Put forward by a reddit user, the theory suggests that just as the Doctor changes his face and personality each time he regenerates, each new incarnation comes with a new name as well.

According to the theory, the faces themselves tended to belong to people the Doctor once knew (in a similar way to how he “picked” the face of Roman citizen Caecilius for his Twelfth incarnation), meaning the “name” attached to each of them becomes the Doctor’s as well.

As a theory it might sound a little odd, but the more we think about it the more it makes sense. We already knew that the Doctor’s entire personality and appearance could change with a regeneration, so who’s to say the complex identity politics of the Time Lords (who can always recognise each other, no matter what they look like) wouldn’t be just as fluid?

The Time Lord concept of a name could be completely different to our own, and their practice of holding on to “nicknames” (like The Doctor, The Master or The Corsair) might be a way of reminding themselves who they really are through a mass of different names and personalities.

Also, the Doctor’s name has occasionally been said to be unpronounceable and difficult even for the Doctor to say due to some emotional trauma. What could be trickier to spell out than a dozen different names taken from over thousands of years, perhaps sometimes coming from dead friends?

Yes it’s a bit far-fetched and will probably be disproved at some point, but let’s get real – in a TV series with a constantly-recast lead character who flies around space and time in a phone box with a rotating female sidekick from 21st century Earth, the idea that said lead might go by more than one name isn’t the most ridiculous idea in the universe.

That, or it’s definitely Basil.