“Graffiti?” said Gale. “We don’t do mindless vandalism.”
“It’s not mindless vandalism,” I said, “it looks like it’s been pretty carefully thought out.” I brought the picture up on screen. Someone had covered a suspiciously blackboard-like wall in an awful lot of maths.
“Bournemouth? That’s your neck of the woods. Don’t try to look innocent!”
I stopped trying to look innocent, but immediately scotched the “Beveridge did it” argument. “You’ve seen my handwriting, right?”
Gale considered this for a moment. “You’re off the hook. So what is it? What does it mean?”
“Gauss only knows,” I said. “It says ‘no vacancies’ in the bottom right. Whether that’s a comment on Boscombe’s housing or employment situation, I don’t know.”
“I can read,” said Gale, dryly. “What about the sums? The sums, Beveridge, the sums!”
“Oh, those. Well, the thing that jumps out is the bit at the top, just to the left of the graph - it’s repeated to the right: \((x^2 - y^2) dx + xy^2 dy = 0\) First order non-linear differential equation,” I said, as if I hadn’t just looked it up on Wolfram Alpha. “And all of those $k$s and $h$s knocking around - they look a lot like some sort of numerical solution scheme.”
“Modified Euler?” suggested Gale, as if he hadn’t just looked it up on Wolfram Alpha.
“Hard to say,” I said. “On the one hand, it looks like fairly advanced maths, but on the other… there are a lot of closed brackets that were never opened, a few $f$s that look like they should be integrals, and some $t$s that ought to be $+$s. I can’t help but wonder if it’s not a mathematician but someone with a photocopy of a page from a maths book.”
“You think it’s not just graffiti, but plagiarism too!?”
“I can’t be sure. It’s an avenue to investigate, certainly.”
“The contour plot in the middle at the bottom - do you think that looks a bit like the plot Wolfram comes up with?”
“It’s a bit of a stretch,” I said, squinting a bit, “but it’s not a terrible call.”
“Can you solve the equation?”
I shook my head, sadly.
“Any idea who could have done such a thing?”
I carried on with the shaking. The phone rang.
“Gale!” said Gale, sharply. “No, that wasn’t a weather forecast.” The other end babbled. “I see. Blown out of the water, you say?” Babble. “OK, thanks very much. We’ll look into it.” He slammed the receiver down. “That was someone from the Mail.”
“I thought the policy was…”
“I know. But there’s been a… development. Look here!”
I skimmed. “Boffins have blown it out of the water? That’s a pretty strong statement when they’ve asked one person and he’s said roughly what we said.”
“I don’t buy it,” said Gale. “Maybe our view… readers can help us out. On the plus side, the Mail has some better pictures than the Echo does. Even though the photographer has clearly roped in locals and said ‘stand in the middle of the whiteboard and do a Stan Laurel.” (Picture 1, Picture 2, Picture 3)
“This is a bit of a rubbish maths police investigation, isn’t it?”
I nodded, and the credits rolled.
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