8. Angel Coulby
Famous for Queen Guinevere "Gwen" Pendragon, Angel Coulby has already worked with BBC Wales extensively so she must surely be in their address book. She gave her character plenty of moments of both emotion and silliness so a transfer to the TARDIS from Camelot would be no problem at all. Also, she briefly appeared in Doctor Who back in 2006 as Katherine, a friend of Madame de Pompadour in The Girl in the Fireplace, which, as luck would have it, was written by current showrunner Steven Moffat. Put in a good word for her, Moff! Since leaving Merlin she has gone on to star in Dancing on the Edge, a BBC drama nominated for three Golden Globes.