Peter Capaldi has revealed which classic companion he’d like to see return to the TARDIS.
Speaking earlier this month at Fan Expo Dallas, Capaldi unequivocally answered:
“Susan. Her story wasn’t finished.” 
Played by Carole Ann Ford, Susan Foreman was the Doctor’s granddaughter and travelled with school teachers Ian Chesterton (William Russell) and Barbara Wright (Jacqueline Hill) from the very first episode in 1963 up until 1964’s The Dalek Invasion of Earth.

She later returned in 1983 for The Five Doctors anniversary episode and *shudder* for 1993’s charity special, Dimensions in Time.
The character of Susan was last seen in the opening moments of The Name of the Doctor in 2013, where she was played by a body double.
Carole Ann Ford visited the TARDIS set during the filming of 2014’s Christmas special, Last Christmas, where she told Doctor Who Magazine that  Capaldi was “running around the TARDIS saying, ‘She’s got to come back! She’s got to come back!’”
Asked at the time if she would return, she replied: “Yeah, of course! Are you kidding?”
So would you like to see Susan return? Would you like to see her story finished? Which other classic companion would you like to see back on board the TARDIS?