The forgotten logbook of a former Royal Navy diver has revealed a fascinating  insight into attempts to raise a unique First World War submarine that sank more  than 80 years ago as the result of a tragic accident.

The faded and yellowing diary was rediscovered by the family of Plymouth-born  Albert “Bob” Smale who, as a 23-year-old recently-qualified navy diver took part  in a year-long salvage operation to raise the world’s very first underwater  aircraft carrier, HMS M2.

Lee Smale, 62, of Plymouth,  the youngest son of four children born to Bob  and Gladys Smale, remembers his father’s logbook from childhood.

He said: “The logbook had always been in the family but we’d never really  given it much thought. He died in 1968 but it was only when we began sorting  through my mother’s things when she moved into sheltered accommodation that it  resurfaced.

The M2 was one of four “M” class submarines put into service during the First  World War and following the cessation of hostilities was modified to carry a  small two-seater Parnell Peto biplane.

Intended for aerial reconnaissance during advance scouting missions, the aircraft had hinged wings to allow it to fit within a specially designed watertight hangar. Launched by hydraulic “catapult”, the Peto was recovered via a deck-mounted crane on its return.

On January 26, 1932, during a routine training exercise off West Bay, Dorset,  after advising her support vessel of her intention to dive, all contact with the  M2 was lost and the submarine disappeared without trace.

A major search ensued but with her position unknown it was eight days before  the M2’s location was eventually discovered.  All of the vessel’s   60-strong  crew lost their lives in the tragedy – believed to be a direct consequence of a  failure to secure the submarine’s hangar doors before diving.

Lying upright on the seabed at a depth in excess of 30 metres, the Royal Navy  salvage team, hindered by the strong tidal currents that swirled around the M2,  worked around the clock for   11 months to seal the hull before filling the  vessel with air to refloat the stricken submarine.

However, as the salvage attempt reached its final stage, and only six metres  from the surface, a heavy gale resulted in the operation being aborted and the  M2 dropped back down to the seabed.

The neat handwritten pages of the logbook initially record Mr Smale’s diver  training, but further examination  revealed a passage dedicated to the M2  salvage work carried out by himself and his colleagues.

Under a heading entitled “M2 Salvage,” Mr Smale describes the “method of  sealing hatches with cement”.

“Hatch is closed down and then a layer of small bags filled with cement is  placed on top, and then a few buckets of loose cement is put on to fill in the  spaces between bags,” he wrote.

The logbook also contains a detailed hand-drawn illustration of the submarine  showing its position, features and amendments before the failed lifting  operation.

The difficulties of working at such a depth, contending with strong tides,  poor visibility and bad weather while dressed in the heavy brass helmets of the  era are also conveyed in detail in a collection of newspaper cuttings pasted  among the book’s pages.

The Dorset Echo newspaper reported: “He has an electric torch swung around  his neck. The feeble illumination of this helps him when the torch is held  close, but his principal asset is a sense of direction acquired by experience  and that astonishing sensitiveness of touch which utter darkness gives to a  diver as to a man who is blind.”

“My dad had quite a varied and distinguished career,” said Lee, who also has  a certificate in recognition of his father’s Mention in Dispatches during the  Wanhsien Incident on the Yangtze River, China in 1926.

Going on to achieve the rank of Petty Officer, Bob Smale was a contemporary  and close friend of Lionel “Buster” Crabb, the Royal Navy frogman who  disappeared in mysterious circumstances at the height of the Cold War.

Lieutenant Commander Crabb, came to prominence for his pioneering work in  underwater bomb disposal during the Second World War and while he had all but  retired by 1955, just a year later he was recruited by MI6 to investigate an  advanced propulsion system used by the Soviet cruiser Ordzhonikidze during the  vessel’s visit to the United Kingdom.

On the evening of  April 19, 1956, Crabb descended into the murky waters of  Portsmouth Harbour on what was to be his final mission and was never seen  again.

Several months later the headless and handless corpse of a diver was  discovered floating in a nearby harbour, but this was not the end of Commander  Crabb’s story.

At the inquest into Crabb’s disappearance, the coroner’s report suggested the  body was in all probability that of the missing 47-year-old OBE and George Medal  holder – despite the lack of firm evidence which could have been provided by  fingerprints or dental records.

Unsurprisingly, various theories abounded as to Crabb’s fate: he was killed  by a Soviet sniper; eliminated by MI5 or even defected to the USSR to head their  military diving team.

However, Lee Smale is adamant that his father’s friend did not die on that  fateful night.

“He and my father were apparently very close and he told members of the  family at the time that he didn’t believe for one minute that Crabb was dead,”  he said.

With her protected status as a War Grave, the wreck of HMS M2 has now become  popular dive site with recreational scuba divers.

Allowed to dive her remains on a “look-but-don’t-touch” basis, the modern-day  diver can observe the M2’s final resting place, just as Bob Smale did more than  80 years ago.