Born at Shooter's Hill, Blackheath, SE, on 24 July 1877, the second son and second child of Colonel Joseph Sladen, RA, JP and DL for Kent and the Cinque Ports, and his wife Lady Sarah Lambart, daughter of the eighth Earl of Cavan. He was educated privately, at Ripple Court near Dover, and at the London Hospital. He held the post of resident surgeon at the Royal Sea Bathing Hospital, Margate, until 1902, when he was appointed district surgeon to the Great Indian Peninsular Railway. He was subsequently PMO on both the Bengal - Nagpur and the Bengal - North Western Railways. In 1929 he became PMO at headquarters on the Great Indian Peninsular Railway. He retired in 1932 and lived at Benclutha, Rotherfield Road, Carshalton, Surrey. He married in 1902 Jessie, daughter of Peter Stuart, the inventor of Stuart's Granolithic. She survived him with a son and a daughter. He died at Folkestone on 15 February 1935, and was buried in Folkestone cemetery. Sladen specialized in surgery, and was active in the prevention of malaria; he was also active in St John Ambulance work in India. He had great administrative ability, was a keen sportsman, and an adventurous explorer on the Tibetan border.