The three-part adaptation of Agatha Christie's Ordeal by Innocence was set to be the BBC's Boxing Day centrepiece.
But after allegations of sexual assault were made against one of its stars, Ed Westwick - which he strenuously denies - it was pulled from the schedule.
The producers then made the decision to reshoot 35 scenes in 12 days with a replacement actor, Christian Cooke.
"Hundreds and hundreds of people's work would have just gone," director Sandra Goldbacher told the Radio Times.
"Or been indefinitely delayed. Which would have been devastating to everyone."
Producer Damien Timmer told the magazine the decision to re-shoot was "mired in sadness" due to the circumstances.
But Goldbacher said she "felt encouraged by Ridley Scott having done it". (Scott re-shot scenes replacing Kevin Spacey with Christopher Plummer for his latest film release, All the Money in the World).
"It was like a sort of talisman for us all: he's done it, so we can do it," Goldbacher explained.
It wasn't an easy task - the challenges included getting all the actors back in (which Timmer says was "very complicated as we had cast very good - and therefore very busy - actors"), reshooting in the winter rather than the summer and re-booking locations.
"There was a fur coat we'd borrowed. And so we had to track down the owner and borrow it back for Anna Chancellor," said Goldbacher.
And how did the performances of Westwick and Cooke, who play aristocrat Mickey Argyll, compare?
"Both performances had weight and integrity but they were very different, which was one of the fascinating things about doing this," said Timmer.
Ordeal by Innocence, which along with Cooke and Chancellor also stars Bill Nighy and Alice Eve, will now be broadcast on BBC One in April.
The first episode will air on Easter Sunday.