[2] à In 1833, Peacock went to London as a medical student at University College, also attending the surgical practice of St George's Hospital.
In 1850, he was elected a fellow of the College of Physicians, and in 1865 delivered the Croonian lectures there on Some of the Causes and Effects of Valvular Disease of the Heart.
A dispensary that he began in Liverpool Street, London, ultimately grew into the Victoria Park Hospital for diseases of the chest, to which he was a physician from its foundation.
He lectured at St. Thomas's Hospital and was one of the founders of the Pathological Society of London in 1846 and a contributor to its Transactions.
On 30 May 1882, while walking in St. Thomas's Hospital, he became suddenly unconscious, fell in one of the corridors, was carried into a ward that was formerly under his care and died there the following day without having recovered consciousness.