By Ken Banks
North East and Northern Isles reporter, BBC Scotland news website
Commander Ralph Lennox Woodrow-Clark was one of the 833 who died
It was one of the darkest days in the history of the Royal Navy.
The WWII conflict was only a few weeks old when, in the early hours of Saturday 14 October, 1939, the battleship Royal Oak was torpedoed by a German U-boat at its base at Scapa Flow in Orkney.
Most of the 1,200 crew were asleep below deck.
The first salvo caught those on board by such surprise that many assumed the impact was instead a problem on board rather than an attack.
HMS Royal Oak was then struck with a second torpedo wave, and the ship capsized within minutes.
Almost 400 crew survived after the Royal Oak sank
Almost 400 of the crew, many badly burned, were saved. However 833 comrades - including many boy sailors - lost their lives.
The German attack was a bitter early blow to the nation's morale.
The tragedy has not been forgotten on Orkney, in the Northern Isles.
The wreck is an official maritime war grave protected by the council. And there is a permanent memorial located inside Kirkwall's St Magnus Cathedral.
On Sunday morning, a service was held in the cathedral, and a parade featuring local dignitaries, the Royal British Legion and youth organisations took place.
Then on Wednesday, the 70th anniversary of the sinking, HRH The Princess Royal is expected to lay a wreath on the water where the Royal Oak sank below the waves.
HMS Penzance will sail to the site of the wreck for the ceremony.
Last year, one of the few survivors of the attack was reunited with his crewmates when his ashes were placed in the wreck by Royal Navy divers.
There is a memorial inside Kirkwall's St Magnus Cathedral
Fernleigh Judge had always wanted to return to the islands to pay tribute to his friends but had been unable to make the journey from his Peterborough home.
Meanwhile, the nephew of one of the Royal Oak victims is also publishing a new book about the sinking.
David Turner, whose uncle - Commander Ralph Lennox Woodrow-Clark - died in the torpedo attack, hopes Last Dawn will help keep alive the memory of those who died for future generations.
He has also been filmed for a video for schools.
He said: "The greatest satisfaction for me is the fact that I have managed to get it into the educational system to teach children, because they need to know what happened."
Sunday and Wednesday's poignant events on Orkney will also go some way to ensuring the hundreds who lost their lives in the dark chapter that was the Royal Oak's sinking are not forgotten.