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 Early references 

The following text has been added and removed multiple times in the last few days.  Is there an consensus as to whether it is worthy of inclusion
The Doctor's twelfth incarnation has been briefly mentioned earlier in the series. In The Ultimate Foe, a serial from the 23rd season (The Trial of a Time Lord), a mysterious figure known as the Valeyard is revealed to be a distillation of the Doctor's darker side, from between his twelfth and final incarnations.

personally I think it is. =>  (Text Me!) "