Doctor Who turned 60 in spectacular style, marking the occasion with three 60th Anniversary specials penned by returning showrunner Russell T Davies, featuring returning stars David Tennant and Catherine Tate. Tennant, best known and loved by Doctor Who fans for his portrayal of the Tenth Doctor, burst back onto the scene in a surprising regeneration that saw him become the Fourteenth Doctor. Tate brought back the Tenth Doctor's best friend and final companion, Donna Noble, who had her mind wiped at the end of her previous adventures with the Time Lord. The duo's return raised a lot of questions and, while the 60th anniversary specials offered some answers, there were many more questions raised along the way.
Source：https://www.cbr.com/doctor-who-60th-anniversary-burning-questions/
