In 1947, Thomas Holmes Sellors (1902–1987) of Middlesex Hospital in London operated on a Tetralogy of Fallot patient with pulmonary stenosis and successfully divided the stenosed pulmonary valve. In 1948, Russell Brock, probably unaware of Sellors's work, used a specially designed dilator in three cases of pulmonary stenosis. Later that year, he designed a punch to resect a stenosed infundibulum, which is often associated with Tetralogy of Fallot.