10 Reasons Why The New Doctor May Actually Be River Song

As mentioned in the previous point, in River's timeline she has not married the Doctor yet. But, if she does know who the Doctor is, why does she not recognise Whittaker?

Well, River has not seen this face. Just as she did not recognise the Twelfth Doctor, she does not know the Thirteenth yet. Or perhaps this is part of River's timeline before the popular portrayal by Alex Kingston. We do not know that River has met the Doctor at all yet - other than as a baby. When she met the Twelfth Doctor, she spoke of how she loved him, meaning that they had already met. As their paths are opposite, River must have met an older regeneration of the Doctor and thus it is possible that she will know Whittaker's Doctor. Perhaps, we have just witnessed the first instance of River meeting the Doctor.

Just as Amy and Rory did not know Mels was Melody Pond, we may not know that Martin is River Song. And just as River does not recognise the Doctor, the Doctor will not recognise River. As far as we have known previously, there were only two regenerations before Alex Kingston's portrayal. However, this may not be true.

This face is unrecognisable to the Doctor and while the Chameleon Circuit is still disguising River's true identity, the sonic screwdriver will not expose her either - the Doctor will not know River until her memory is fully restored.