Six hundred and ninety-two prisoners arrived in Australia under the care of Robert Armstrong. In all thirteen men died under his care, this high number being because of the ten men who died of scurvy during the long voyage of the Tottenham.
He was appointed to Plymouth Hospital in 25 February 1829.
The Influence of Climate and other Agents on the human Constitution, with reference to the Cause and Prevention of Disease among Seamen; with Observations on Fever in general and an account of the Epidemic Fever of Jamaica in 1843.
Royal College of Surgeons
Robert Armstrong is on the list of Fellows of the Royal College of Surgeons in 1844 (at Plymouth Hospital)
In August 1847 it was announced that Robert Armstrong had been promoted to the rank of Medical Inspector and appointed to the Royal Hospital Plymouth vice Sir David J.H. Dickson M.D. who had retired. Armstrong was replaced as Deputy Medical Inspector at Plymouth Hospital by Dr. Oliver Evans who had previously been stationed at Bermuda Hospital 
Two years later a correspondent to the Daily News in March 1849 explained in part the cause of Robert Armstrong's dismissal from this position: .......Since the popular determination for financial reduction has become evident, the naval authorities, to prove their sincere desire to comply with the wishes of the times, have decided on not filling up two vacancies among the deputy inspectors which have lately occurred, although senior surgeons expect advancement in such cases. Dr. Lindsay, deputy inspector from half pay is appointed to the vacancy at Malta Hospital vice Dr. Watt, deceased. At the Plymouth Hospital Dr. Armstrong Inspector of hospitals is dismissed and a medical officer, with the title and pay of surgeon is to do the duty of this inspector.......
He is listed in the Medical Directory of England for 1853 -
Hill's-court, Exeter - M.D. Edin. 1825;
F.R.C.S. (Nom) 1843; M.R.C.S.E. 1816;
F.L.S; Inspector of Hospitals and Fleets;
late Phys. royal Naval Hospital Plymouth.
Author of The influence of Climate on the human Constitution; The Epidemic Fever of Jamaica.
Robert Armstrong died at Hill's court, Exeter age 63 28 June 1855