HMS R4

HMS R4 was a British R class submarine built at Chatham Dockyard. She was laid down on 4 March 1917 and launched on 8 June 1918. R4 was commissioned on the 23 August 1919. She came too late to see any combat in World War I, like most of the other R class submarines. The submarine's shape resulted in her being nicknamed "The Slug".

R4 was the only boat to survive through to the 1930s. Additions to her casing produced slightly better sea keeping at the cost of a reduced speed from 15 knots submerged to 13 knots. R4 was used as a fast underwater target at the Portland anti-submarine school until 1934, then sold on 26 May 1934 to Young, Sunderland.