William was born in Tettenhall on 20 October 1882. He was the elder son of William Henry Underhill of Parkdale, Wolverhampton. He was taught at Repton School, where he was boarding in 1901.
He became a Lieutenant in the Worcestershire Regiment. On 10 May 1914, he took his Royal Aero Club Aviators’ Certificate at The Vickers School, Brooklands. He was killed in action on 21 October 1914. He was mentioned in despatches in the London Gazette on 17 February 1915. The Express & Star carried a notice of his death on 22 September 1916. William is remembered at the Le Touret Memorial in France.