Born on 12 December 1860, the eldest son of Edward Waldy of Barmpton, near Darlington, and Jane Chiesman, his wife. The second son, a solicitor, was more than once mayor of Darlington. John Waldy was educated at Pemberton School kept by the Rev Christopher Jackson at Middleton St George, Co Durham, and on 1 October 1877 joined the Medical School at Newcastle-upon-Tyne, which was the medical faculty of the University of Durham. He was appointed an assistant demonstrator of anatomy in 1881, jointly with William Robinson, FRCS, before either was qualified. In October 1881 he entered St George's Hospital, London, where he acted for some time as assistant medical registrar. He then returned to Newcastle, became house surgeon for two years at the Royal Infirmary, and for another two years was house physician, being the last resident to be appointed without a time limit. In both positions he proved himself an excellent clinical teacher and a firm disciplinarian. As house physician to Sir George Hare Philipson, then senior physician and a character, he had many stories to tell. As soon as Waldy had obtained the FRCS he began to practise at Catterick in partnership with John Hanley Hutchinson, who had been a pupil of Sir William Gowers. The practice soon extended over thirty villages and required eleven or twelve horses to work it, much of the ground being covered in a high gig driven tandem. The round often began at 8 or 9 o'clock in the morning and was not completed until late in the afternoon. Waldy would then dine, order the medicines he had prescribed to be made up, and instantly fall asleep in front of the dining-room fire, where he remained until the maid came in the next morning. This habit he continued even after his first marriage. In 1899 he began to use a brougham drawn by a pair of horses, which was replaced about 1911 by a motor car. During the war he acted as surgeon to a VAD convalescent home for sick and wounded soldiers, and during the last years of his life he gave up general practice for consulting work. He married twice: (1) in 1893 Alice Elizabeth, second daughter of Valentine Rippon, JP, of Rogerley Hall, Frosterley, Co Durham; she died 24 December 1930; her elder sister married William Robinson, MD, FRCS, of Carlton House, Sunderland; (2) on 13 June 1933 Annie Simpson, who survived him without issue. He died at his home, 1 Green Park, Darlington on 25 April 1937. His ashes were buried in the churchyard of Haughton-le-Skerne. Throughout his life he was a total abstainer, and he disliked tobacco. He was held in high esteem by his colleagues for his honesty and thoroughness. His remarkable memory enabled him to recall similar cases which he had seen many years previously. His treatment was simple, for he usually said to the patient: "Go to bed, and take two or three glasses of nice hot milk every day," so that he was known by the soubriquet "Go-to-bed Waldy". Waldy left £1,000 each to the Royal Victoria Infirmary, Newcastle-on-Tyne, St George's Hospital, Westminster Hospital, and Darlington Municipal Hospital; and he left land, known as Green Park, to the county borough of Darlington, to be kept as a public recreation ground.