The show executive producer was revealed the festive special was thrown into doubt when he announced he was leaving, and faced being dropped from the schedule altogether.
Steven told Digital Spy that his last episode was originally meant to be the finale to the most recent series, but he was persuaded to stay on when he realised new boss Chris Chibnall would not be starting his tenure with a Christmas special.
“Then I learned at a drinks event somewhere that Chris didn’t want to start with a Christmas, so at that point they were going to skip Christmas. There’d be no Christmas special and we would’ve lost that slot,” he said.
Steven added that he then had to persuade Peter Capaldi, who is also leaving his role as The Doctor, that ’s how they would depart the show.
The Christmas special was later confirmed, and trailer for the episode - which will also feature new Doctor Jodie Whittaker - debuted last month.
Entitled ‘Twice Upon A Time’, the special will see the Doctor team up with his very first incarnation, who made a surprise appearance during the series finale earlier this month.
The trailer shows the pair uniting to fight a new dark force, while there is also shots of an appearance from Mark Gatiss, who will play a first world war soldier known as the Captain.
Assistant Bill Potts will also return for Peter’s farewell as the Doctor, but actress Pearl Mackie has also revealed this will mark her last appearance.
Rumours have also suggested former companion Clara Oswald (Jenna Coleman) will make an appearance in the Christmas special to mark the end of this era of the show.