The short version (TL;DR): Dave Trott's Crossover Creativity argues that new ideas come from colliding things that don't belong together, and that most of us get stuck trusting averages, metrics and labels. This review retells the book as a fable, starring a retired Grand Prix mechanic who teaches an evening repair class to four students who each get one thing wrong. My honest review, four stars out of five, is at the end.

It began, as these things often do, with a spreadsheet.

Marcus brought it to the first class, printed on eleven sheets of paper and held together with a bulldog clip. It tracked every bolt he had ever tightened.

The class met on Thursday evenings in a draughty garage that smelled of oil and tea. The teacher was Dot, who had spent twenty years in the pits of Grand Prix racing and now ran a night class called Fix Anything.

"I don't teach repairs," she told the four of them. "I teach noticing."

On the bench sat a wine bottle with a cork rattling around inside it. Nobody asked about it. Dot didn't explain.

Priya

Priya had measured eleven hundred customers for her chair business and built one chair for the mean of all of them. She was very proud of it.

"Sit," said Dot.

Priya sat. Her knees hit the table. Marcus sat. He sank. Tobias, who was six foot four, perched on it like a heron.

"It fits nobody," said Marcus.

"Hm," said Dot. "Early in the 1950s, the US Air Force measured 4,063 pilots on ten dimensions. Height, chest, sleeve length. It wanted to build the perfect cockpit for the average pilot."

She waited.

"A young man named Daniels checked how many pilots were actually average on all ten."

"How many?" said Priya.

"None. Not one."……

Dot pulled a lever under the seat. It slid back with a clunk.

"So they invented adjustability. The seat height, the legroom, the angle. You can look at that lever as the average being told it doesn't exist."

Priya looked at her chair for a long time.

Marcus

"Right," said Dot. "A game. For every bolt you tighten, you get a point. Most points wins a biscuit."

Marcus's eyes lit up.

Ten minutes later, Tobias had tightened, loosened and re-tightened the same bolt forty times and was leading comfortably.

"I've gamed it," he said, with some pride.

"You have," said Dot. "A man called John Nye told Trott about the vending machines at Ford. They only took 10p coins, and they weighed and measured each one exactly. Some workers spent hours machining fake coins to that tolerance. On piece-work, half a day cost them about £2 in wages."

"To save 10p," said Priya.

"People will always game the system, any system. And a general named McNamara did it with a war. He picked one number, the body count, and promotions followed it. Eventually he admitted the figures were 'grossly in error.'"

Marcus put down his clipboard. He did it slowly, like a man setting down a pet.

"The biscuit tin," said Dot, "is the metric. Whoever gets the biscuit is not necessarily whoever fixed the car."

Tobias ate the biscuit anyway. Dot let him.

Lena

Lena owned fourteen spanners, all from the same expensive brand, and had never used thirteen of them.

Dot opened two identical toolboxes on the bench. One had a gleaming silver label reading Palessi. The other said Payless.

"Which would you pay more for?"

"Palessi," said Lena at once.

"Same spanners. Same factory." Dot closed the lids. "In 2018, a discount shoe chain opened a fake luxury store in Santa Monica. Grey walls, gold mannequins, champagne. Fashion influencers paid hundreds of dollars a pair for shoes that cost between $19.99 and $39.99. And none of them could tell."

Lena looked at her toolbox.

"Hold up a cigarette," Dot went on, "and say 'Dunhill,' and people picture leather armchairs. Say 'Marlboro,' and they picture cowboys. Same tobacco. That's context. Half the taste is in the packaging."

"So what do I do?" asked Lena.

"Use the thirteen."

Ten Minutes Later

Tobias had repaired clocks for thirty-one years. He had never fixed anything that didn't tick.

"Open that," said Dot, pointing at the bottle. "The cork is inside. Without breaking the glass."

Tobias tried tweezers. A magnet. Tipping. Shaking. He tried, in desperation, apologising to the bottle.

Nothing worked.

Lena, who had been eating her lunch, held up the plastic bag it came in. "Would this help?"

Dot said nothing for a moment.

"A mechanic in Argentina called Jorge Odón saw this trick online. You twist the bag long and thin, thread it in, blow it up. The cork pins against the glass. Out it comes."

Tobias did it. The cork popped out onto the bench.

"Then at 4 a.m. one night," Dot continued, "Jorge woke up and thought, what if the bottle is a birth canal and the cork is a baby? He built the first prototype in his kitchen. A glass jar for the womb. His daughter's doll for the baby. A bag his wife sewed."

"You're joking," said Priya.

"It became a real medical device. That's recombinant thinking. New ideas aren't made from nothing. They're what happens when two things from different worlds bump into each other."

Tobias held up the bag. "A clockmaker and a lunchbag," he said, wondering.

The Showcase

On the last night, the class held a race. Four ride-on lawnmowers, once around the yard.

Halfway round, Tobias's mower began to leak oil.

He knew at once what it meant. He had listened to ticking things for thirty-one years. The pressure drops on the bends, because the turning flings the oil away.

So he did what Dot had told them about in Week Three. In 1965, at the British Grand Prix, Jim Clark's oil pressure was dropping on the corners. There was no radio, so his team boss didn't know. Clark took the power off through each bend and crossed the line 3.2 seconds ahead.

Tobias took the power off through each bend. His mower coughed, squealed and crept home.

He finished second.

"A," said Dot.

"But I lost!"

"You made the right decision with the information you had. The result is a different question."

Priya's mower, adjusted to her exact height, came third. Lena used all fourteen spanners and finally learned why they had different sizes. Marcus did not keep score.

Then there was the fence at the bottom of the yard.

"Tear it down," said Lena. "It's in the way."

"Do you know why it's there?" asked Dot.

Nobody did. It's an old principle: Chesterton's Fence. Before you pull down a fence, find out why somebody built it.

They found out. Behind it, hidden by brambles, ran an open drain.

Garage Radio, 6 p.m.

Priya has measured another eleven hundred customers.

Marcus has stopped counting bolts. He is now counting biscuits.

Lena was seen buying a toolbox with no label. She asked for a receipt.

Tobias has repaired a clock using a lunch bag. He has been asked not to say how.

The fence remains.

Dot's Journal

Anyone can learn to fix a thing. The difficult part……is knowing what is actually broken. It is rarely the part you are holding.

The average does not exist. The score is not the game. The label is not the spanner. The answer is often in someone else's toolbox.

And before you tear anything down, find out why it was built.

What fence are you about to knock over?

So, what did I think of the book?

I gave Crossover Creativity four out of five stars.

Trott's strength is that every idea comes dressed as a story, and the best ones stick: Jorge's cork, the cockpit that fit no one, the shoes that weren't Palessi. You can open it anywhere, read four pages and have something to repeat at dinner.

The weakness is the flip side. A few pieces, like the fuss over cream in carbonara and the armoured-car money blowing across a California highway, felt to me like they were making a point the book had already made better. And because the chapters are so short, the promised thread of "crossover thinking" sometimes frays. You do the crossing yourself.

Buy it if you like your lessons as short stories. Skip around if you don't.

The ideas in this story come from Dave Trott's Crossover Creativity. The characters are fiction; the studies and stories are real.

Story format inspired by Mihir Misra's "The Tiger Teaches Photography."