On 19 April 1858, a committee was formed by members of the Mercantile Marine Service Association (M.M.S.A.) to establish a training ship on the Mersey, to train boys to become officers in the Merchant Navy. The Admiralty offered the frigate Conway, a coastguard ship at Devonport which, on its arrival in the Mersey, was moored off Rock Ferry. The school was opened on the 1 August 1859.

The original Conway was replaced after two years by HMS Winchester (renamed Conway) and in 1876 she was in turn replaced by HMS Nile, a vessel designed by Sir Robert Seppings, one of Britain's finest naval architects. She remained in the Mersey until 1941 when she was moved to the Menai Straits to avoid the Blitz. In 1953, whilst being towed to Birkenhead for a refit, she was grounded near the Menai Suspension Bridge and broke her back. Soon after she caught fire and had to be broken up.

From 1953 to 1974 the HMS Conway Cadet Training School flourished as a shore establishment based at Plas Newydd, Anglesey, and in 1968 the school was given voluntary aided status. The British Shipping Federation (B.S.F.) took responsibility for the nautical training and placements, while Cheshire Education Authority assumed charge of the general education side. However, its closure was precipitated by the decline of Britain's Merchant Fleet, and on the 11 July 1974, the last 85 cadets laid up the Colours in Liverpool's Anglican Cathedral.

The average time spent by Conway cadets was two or three years. They normally entered between the ages of 12 and 15 years. Eminent cadets included John Masefield (1891-1953) who wrote the Conway's history in 1933 and again in 1953; Captain Matthew Webb, the first man to swim the channel in 1875; Kenneth Shoesmith, marine artist (d.1939), as well as many eminent captains.