Roald Dahl is best remembered as an author of children’s books, particularly for works like Charlie and the Chocolate Factory and Matilda. His stories have sold more than 250 million copies around the globe.

But Dahl was much more than a storyteller: He also helped invent a medical device that has been used on nearly 3,000 children worldwide, according to an interview with his daughter, Ophelia, published this month in The New Yorker.

In 1960, Dahl and his first wife, Patricia Neal, were visiting Manhattan when their four-month-old son, Theo, was hit by a cab. Theo was being wheeled in a carriage by his nanny and when the car hit him, Theo and the carriage flew forty feet in the air. His skull shattered upon landing.

At the hospital, Theo needed multiple surgeries and doctors used a traditional shunt to drain the fluid accumulating in his brain. But the shunt used to relieve him of hydrocephalus kept getting blocked by debris. So Dahl made a few calls.

He contacted Stanley Wade, a friend who designed engines with tiny hydraulic pumps for model airplanes, as well as Dr. Kenneth Till, a pediatric neurosurgeon. Together, they came up with the Dahl-Wade-Till shunt.

The device was specifically designed to resist retrograde flow. In The Lancet, Till reportedly described the shunt as having “low resistance, ease of sterilization, no reflux, robust construction and negligible risk of blockage.”

In her interview with The New Yorker, Opehlia remembers there being a prototype of the Dahl-Wade-Till shunt hanging on the walls of their home in Buckinghamshire.

“Funny old thing – looked like the inside of a watch,” she told the news outlet. “He never talked about it with us. But my father never talked about his accomplishments. He did none of that boring stuff that people who look back on an accomplished life do.”