Doctor Who: 14 Cool Details In Steven Moffat & David Tennant's Silence In The Library Commentary
12. This Scene Is Complete "Waffle" That Was Only Added To Make The Episode Longer
Sticking with this same scene, Moffat states that it "goes on a bit without really getting anywhere", and that's because the episode was initially too short.
It's strange to think that Doctor Who writers are even capable of making an episode too short. With such a tight runtime - and tons of ideas and storylines to cram into said runtime - you'd think that most episodes would need to be trimmed, not expanded.
And yet, Moffat mentions that he "had to add an awful lot of waffle" to get Silence In The Library up to the right length. He made this opening scene between the Doctor and Donna longer, and also fleshed out Miss Evangelista's death scene - specifically, the bits where Donna talks to her while she's dying.
Interestingly, Silence In The Library wasn't the first time - or the last time - that a Moffat script has been too short.
As mentioned in this very commentary, Series 1's The Empty Child was also too short, and two years after recording this commentary, The Time Of Angels would also end up being too short - although, in the latter case, that was because a planned shoot had to be cancelled due to some bad weather.