| Name: | H 42 |
| Type: | Submarine |
| Keel: | 21/09/1917 |
| Launched: | 21/10/1918 |
| Completed: | 18/05/1919 |
| Builder: | Armstrong, Whitworth & Co |
| Yard: | High Walker |
| Yard Number: | 941 |
| Dimensions: | 440disp surf, 500disp subm, 164.6 x 15.75 x 11.30ft |
| Engines: | 2 x Oil engines, 480hp; 2 x Elecric motors 320hp |
| Engines by: | Ruston & Hornsby, Lincoln |
| Propulsion: | 2 x Screws, 13.0knots surf, 11.0knots subm |
| Construction: | Steel |
| Armament: | 4 x 1 x 21.0ins bow torpedo tubes |
| History: | |
| 18/05/1919 | British Royal Navy |
| 23/03/1922 | Sank |
| Comments: | Member of the Admiralty H Class of submarines |
| 23/03/1922: Sank after a collision with HMS VERSATILE | |
| off Europa Point, Gibraltar, with the loss of all of her 26 crew |
Above photo is copyright of the Imperial War Museum