A witness to a submarine tragedy more than 80 years ago has attended the annual memorial service to the 32 men who died in the accident.

Amy Bachelor, from Helensburgh – who celebrates her 100th birthday this year – was on the shore of the Gareloch and saw the rescue operations after K13 sank during trials on January 29, 1917.

One of the notorious K-class submarines, which quickly won a reputation as a jinxed design, K13 was a big advance in submarine technology for the time.

The K-boats displaced 2,600 tons and were 334ft long, and were designed to operate with the Grand Fleet, keeping pace on the surface with the battleships and cruisers which they were to accompany.

In order to provide the speed required when surfaced – up to 26 knots - K-boats were powered by steam turbines, which presented major design headaches as the boilers required two funnels to vent exhaust gases and steam.

As such the hulls of these giant boats were pierced by numerous vents, hatches and other assorted holes, so that submerging became something of a marathon – the funnels, for example, had to be lowered and the gaps made watertight before the boat could dive.

Whereas one of the contemporary H-boats could dive in 30 seconds, it took an average of five minutes for a K-boat.

K13 had already made a successful two-hour dive on the fateful day and been accepted by the Royal Navy.

But Admiralty officials on board decided that before she returned to the dock at her builders, Fairfields, she should make a brief dive in order to verify that the funnel covers and boiler room ventilators were completely watertight.

As she prepared to dive, the crew checked that instruments confirmed al hatches were shut – but the four boiler room ventilators had been left open.

All her aft compartments flooded, swiftly sending the boat to the muddy floor of the loch, 55ft down.

It is though that the 32 victims drowned almost immediately, while a further 48 remained alive in the unflooded forward compartments, where it was calculated that they had sufficient oxygen for around eight hours.

A desperate rescue operation was launched to raise the stricken submarine, but it was 15 hours before an air supply could be provided – and around 54 hours after the accident that the first of the survivors, in a poor state of health, started wriggling through a hole cut in the hull as soon as the bows broke through the surface of the water.

The King sent a message through the Admiralty to congratulate the survivors on their “marvellous escape” and those who “by their untiring efforts rendered their escape possible.”

He also expressed his deep sympathy for the relatives of those, including Fairfields staff, who had died.

It was not until the middle of March that the submarine was raised properly and the bodies of the dead could be recovered.

The body of Cdr Goodhart who, with Lt Cdr Herbert, had attempted to escape through the conning tower in order to provide information for the rescuers, was not found for two months. Herbert was rescued by the crew of a diving boat.

The victims were buried at Faslane Cemetery, where the memorial service was conducted by the Rev David Yates, Chaplain to the Faslane Flotilla and Honorary Chaplain West of Scotland Branch of the Submariners Association.

Also in attendance was the current Captain Faslane Flotilla, Capt Jim Boyd, and his predecessor, Capt Pat Walker, as well as Flag Officer Scotland, Northern England and Northern Ireland (FOSNNI) Rear Admiral Nick Harris and the Director Naval Base Clyde, Commodore John Borley.

Helensburgh Sea Cadets tolled the K13 bell once for every man who lost his life in the accident.

Other K-class boats featured in a litany of disaster throughout their service career. A total of 17 K-boats were completed during World War I; eight suffered disasters, and there were 16 major accidents along with numerous lesser mishaps.