HMS H29 was built by Vickers at Barrow-in-Furness. She was laid down in March 1917 and commissioned in September 1918. On 9 August 1926 she was conducting post-refit trials on her torpedo discharge system in 2 Basin at Devonport. The trial required the boat to trim down aft however both the forward and after hatches were left open.

The main ballast tanks were flooded to lower the boat, but water soon began to flow through the after hatch and, when an attempt was made to shut it, a tube allowing air into the boat blocked it. This tube could not be removed in time and the submarine sank in less than two minutes. Orders were given to clear the boat and blow the tanks and almost everyone made it off, leaving onboard five dockyard workers and Chief Engine Room Artificer, who heroically remained at his post blowing the tanks.

During the incident Lt. Frank H. E. Skryme, the commanding officer, had ordered the watertight doors closed, which may have been the cause of the casualties. According to Surgeon-Commander Alfred B. Cox who autopsied the crew, they all died of suffocation and not drowning. There seems to have been little thought that anyone in the boat had survived the sinking, and there seems to have been no immediate attempt to rescue anyone trapped inside. Most attention appears to have been focused on raising the boat, which was not accomplished until 12 August, far too late for the poor souls inside H29. Their bodies were not removed until 13 August.

Two officers faced charges following the incident. Commanding officer Skryme was found guilty of negligence for omitting to take charge of the submarine and for failing to have a clear understanding with his First Lieutenant as to what that officer’s intentions were as regards to trim. 1st Lt. Malcolm Wevell was found guilty for negligently or by default hazarding H29.

H29 was never placed in commission again and was sold for scrap in October 1927.