Fun behind-the-scenes tidbit, that little reaction shot of Lewis was an extremely late addition. You can tell it was a late addition because it’s basically his face slightly offset and given a change of expression, but the scene had no punch without it.

↓ Transcript
Panel 1:
Russell speaks with pleasant confidence, but what he says attracts the confusion of everyone in the carriage.

RUSSELL: Yeah, she clocked off same time as the other teachers. Said she left your phone behind for you.

RUSSELL: Far as I know, she’s fine. Found a job at another school.

Panel 2:
The others crowd around Russell, crossing their arms with Si. They smell a rat.

RUSSELL: ...did I say something wrong?

BAYANI: Mayweather’s on this train. With us. She’d been stuck out here for decades in crazy-time.

NANCY: She’d been reality-wiped the night of the explosion. Nobody except Si remembered she existed!

Panel 3:
Russell realises he’d done goofed, he’s sweating buckets.

CHAMBERS: So how could you have possibly known she “found a job somewhere else”?

CHAMBERS: What aren’t you telling us, sir?

Panel 4:
Russell reacts badly to this line of questioning, but he’s able to think quickly on his feet.

RUSSELL: I thought she was another imaginary friend! I wanted to spare the feelings of a little girl!

RUSSELL: How was I supposed to know she was wrapped up in yet more quantum nonsense?!

Panel 5:
Russell calms himself and pulls out a notebook, but no matter how hard he asserts his authority his stature has undeniably diminished.

RUSSELL: Whatever. She’s found her way back to existence, I’m very happy for her, now how about we do the same?

RUSSELL: Constable...Chambers, wasn’t it? I have a radio frequency here that will guide us back to King’s Cross Thameslink, could you take me through to the driver?

CHAMBERS: She’s at the other end of the train, sir, wouldn’t it be easier over the intercom?

Panel 6:
Russell leans in and whispers in Chambers’ quizzical ear.

RUSSELL (small): No, because we need to radio ahead to make sure a riot squad is there to take Brilligan into custody.

RUSSELL (small): Now will you stop with the questions that have really obvious answers and hop to it?

CHAMBERS: ...excuse me, sir?