While playing Henry V, Hardy developed an interest in medieval warfare, and in 1963 he wrote and presented an acclaimed television documentary on the subject of the Battle of Agincourt. He also wrote two books on the subject of the longbow, "Longbow: A Social and Military History" and "The Great Warbow: From Hastings to the Mary Rose" with Matthew Strickland. He was one of the experts consulted by the archaeologist responsible for raising the "Mary Rose". He was Master of the Worshipful Company of Bowyers of the City of London from 1988 to 1990. In 1996 he was elected a Fellow of the Society of Antiquaries.