The Wade-Dahl-Till (WDT) valve is a cerebral shunt developed in 1962 by hydraulic engineer Stanley Wade, author Roald Dahl and neurosurgeon Kenneth Till.

Cerebral shunts are used to release excess buildup of cerebrospinal fluid which could result in serious complications (see Wiki article on cerebral shunts).

Under certain conditions, the shunts being used at the time were prone to jamming shut due to debris being clogged in the valves. Which was the case with Roald Dahl’s son Theo, who was hit by a car and suffered bleeding in the brain.  These new shunts had “low resistance, ease of sterilisation, no reflux, robust construction, and negligible risk of blockage”.

Theo had healed by the time the shunt was perfected, but it helped thousands of other children with similar medical conditions.