“Well. The brand is rare. The company was only set up in November 2019, and there was a distribution issue when the supermarket they were partnered with reneged on the deal. So, this company had a big warehouse full of the stuff and needed to shift it.”

I worry that he’s going down a rabbit hole now. “So…” I say.

“The company offered an online special through a Facebook campaign—one hundred packages for fifty pounds.”

“Bargain,” Jemima deadpans and rolls her eyes. “But who cares?”

“Why would a multimillionaire buy bulk discount toilet roll?” Derek asks with glee, clearly thinking that he may just get one over on this bitchy woman who has been taking the piss out of him.

“I assume you have an answer?” I reply.

Derek takes a page from the top of the stack and almost makes a “ta-da” gesture. “She wouldn’t. But Mrs. Valma Hardcastle of Tunbridge Wells loves a good bargain.” The page he has revealed shows a grinning older woman with a huge pile of toilet rolls in the background. A Facebook post liked by all her friends at the WI, or whatever it is that Mrs. Hardcastle does for fun. “Chris’s mum.”

I look at the printout. The post is dated December 2019. I smile.

Jemima leans over my shoulder and taps at the page. “I don’t get it. So what if Chris’s mum bought a job lot of loo roll?”

“How would it end up at Leah’s place?” I use my teaching voice and turn round to look at her. Her cheeks are starting to pinken as she struggles to find the link I have made and even the work experience boy has figured out.

“Chris was having an affair with Leah. He probably gave it to her.” She doesn’t sound convinced of her own argument.

“Does your boyfriend bring you gifts of loo roll?” I ask, and the pink on her cheeks blazes to a vibrant red. We don’t talk about her boyfriend, some chinless wonder her daddy wants her to marry. He’s the reason it’s only a quick handjob she’s giving her boss, although I think after the gusset-flashing earlier, I might be getting an upgrade to a blow job. She won’t let me touch her though; that’s cheating in her book. I don’t argue with her logic.

“Of course not,” she says hurriedly.

“So, how else might it have got there?” My teaching voice now a little more patronizing than before.

“Umm…”

“Because Megan took it there,” Derek interjects, bored. “Remember that week before lockdown when you couldn’t buy toilet roll or hand sanitizer for love nor money? She probably just grabbed a pack from home.”

“I still don’t get it.”

“If Megan took toilet roll to Leah’s house, it proves Chris’s story that Megan was pretending to be Leah.”

“Oh,” she says as the penny finally drops. “But it’s not really proof, is it? I mean, we couldn’t use it in court.”

It’s circumstantial at best. It might throw the tiniest sliver of doubt into the minds of the jurors, which might be enough but most probably would not.