Maths Police Investigates: The Case of The Clotted Cream Formula

"Fancy a Bob Marley doughnut?" asked Constable Gale.

I sighed. "And that's a doughnut…"

"Wi' jam in."

It's a delicate line to draw, with Gale's jokes: laugh too little, and you won't get a doughnut. Laugh too much and he'll tell you another one.

"Speaking of jam," I said, "this one's come in over the wires."

"Rowlett's not going to like that," said Gale. "It's got boffins in."

"Plus it's in the Daily Mail." One of our least reliable sources, frankly. "And it's a 'perfect formula for…' article."

"We've tried to nail the Mail for those before, and never got anywhere. Maybe when they replace the PCC with something more worthwhile."

I played my trump card. "It's about cream teas."


"I agree. We have to stamp on this. I've got tickets on the next train."

"This isn't Cornwall," said Gale. "It's about the polar opposite of Cornwall, actually."

"But this is where the researcher is based," I said.

"Whoever heard of a Yorkshire cream tea!?"

The suspect's name was Dr Eugenia Cheng, a category theorist at the University of Sheffield. Her alleged crime? Shilling for Big Clotted Cream. You see it a lot: mathematicians get down on their luck, and before you know it, Go Compare! are asking you to do them a little favour. From there, it's a slippery slope to seeing your picture next to a Mail article about the perfect formula for a great holiday.

"I think there's more to it than that," said Gale, after allowing the article to pass in front of his eyes again. (He refuses to read the Mail.) "Look at these equations. What do you notice?"

"Great Scott!"

"Exactly! They're dimensionally consistent."

We both sat down. This was a blow.

"There's a one in there, and a half, messing about with distances," I ventured, after a while.

"I still think there's more to it. Is there a link from the Mail article to the original paper?"

Once we both stopped laughing, we set Constable Google on the case. It turned up an actual paper. Not published, but still, halfway credible. In any case, where would you submit it? There's not a Journal of Advanced Afternoon Tea Dynamics1.

"She draws correct conclusions," I said, after skimming it. "Clotted cream rather than whipped cream. And on top of the jam, like civilised people eat. The dimensions check out, too: she says it's all in centimetres."

"Bad form," said Gale, "but hardly the crime of the century. Although the Mail have changed it all into millimetres."

"Surprised they'd deign to acknowledge the metric system."

"Wait, I've got something!" Gale looked up from his phone. "Got a tweet from @jjaron, who is Jacob Aron in real life. Says to check out what happens when $r=1$."

"A two-centimetre scone requires infinite cream! That's a violation of the law of conservation of cream, right there! Ah, but no, hang on, she covers that."

"You can't have a scone smaller than 3cm in diameter because the cream gets thicker than the scone, which is all out of whack," said Gale.

"Don't see a problem with that, myself."

"So, she's covered herself by even giving a range of possible radii? She's good."

"We're on a wild goose-chase here, Sarge. Unless we're going to go after this Weinstein-du Sautoy case as well…"

"You know we can't do that," said Gale. "You're right, though - there's a paper here, and it's pretty good. Plus, it doesn't thank a clotted cream company for funding."

"It wouldn't," I said, checking out her website. "There is no clotted cream in Sheffield. She had to clot her own."

Gale looked at me, horrified. "No clotted cream?" He shuddered. "I think this is one of those cases…"

"Best left unsolved?" I said.

He nodded, and we headed back to the station.


Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008. He lives with an espresso pot and nothing to prove.

  1. so far as we know []


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I teach in my home in Abbotsbury Road, Weymouth.

It's a 15-minute walk from Weymouth station, and it's on bus routes 3, 8 and X53. On-road parking is available nearby.

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