According to BBC News’ Entertainment correspondant Lizo Mzimba, and via his twitter account, the new Doctor Who assistant will be 21 year old Karen Gillan (who previously appeared in the Fires of Pompeii episode as Soothsayer).
Note: BBC News have just published an article on this story now too 🙂
Notes on Soothsayer
Soothsayer is a member of the Sibylline Sisterhood that were in Pompeii in 79 CE. She has eyes painted on the back of her hands – a sign of a soothsayer. She was the first of the Sisterhood to see the TARDIS or “Blue Box” that had appeared in a prophecy. She had psychic powers due to breathing in dust from Vesuvius that was converting her into a Pyrovile and could see time thanks to the rift activity there. It is likely that she died during the eruption as it has not been shown otherwise.
NB – I do not know if her assistant will be an extension of Soothsayer or whether she will be a completely different character – I think that they could go either way with it!
Worth noting that Gillan is being brought in for Matt Smith’s doctor, and that the character of Adelaide (portrayed by Lindsay Duncan) is being brought in especially for the Waters of Mars special. Whilst her time on the show has not been confirmed by the BBC, in light of today’s announcement, I presume we can assume it is just one or two of the special episodes… (?)