THEY were the most powerful battleships Germany had ever built, their 1,000-man crews and 34 guns designed to make sure Britannia no longer ruled the waves.

Almost exactly a century ago the four great Koenig-class dreadnoughts of the imperial high seas fleet unfurled their flags, opened their seacocks and slowly, but unstoppably, sank to the bottom of Scapa Flow.

Their scuttling – and that of another nearly 50 ships into Orkney’s huge natural harbour – was the greatest single loss of shipping on a single day in world history. Their admiral had ordered them sunk on June 21 just as the victorious allies of the Great War squabbled over who should get them.

Now, a hundred years on, the ships are up for grabs again. Or at least three of them are. Their wrecks, officially historic monuments, are up for sale: for £250,000 each, along with a cruiser for £60,000.

The haul – dreadnoughts SMS Kronprinz Wilhelm, SMS Konig and SMS Markgraf and the smaller Karlsruhe – are being advertised on eBay as “a sizeable naval fleet amongst the largest in the world”.

Current owner Thomas Clark, 70, is a retired diver. He hopes the ships will be taken on by someone with a vision for their future.

The Tayside-based diving contractor bought them from a salvage firm for an undisclosed sum in 1981.

Mr Clark said: “It has been an absolute pleasure to own and dive on these iconic vessels and I regret I have not managed to do more with them during the period of my ownership.

“I look forward to passing them on to the new owner and hope they get the opportunity to realise their aspirations for the vessels.”

He purchased SMS Markgraf – the best preserved of the vessels – with the intention of carrying out commercial salvage. The official status of the wrecks prevented him from doing so.

The ships went down to the tolling of a bell on the deck of the battlecruiser Von der Tann, then one of the fastest large warships afloat. The bell is to return to Orkney this week as the centenary of the scuttling is marked – and to be rung by Yorck-Ludwig von Reuter, grandson of Rear Admiral Ludwig von Reuter, the man who ordered the sinking.

The Von der Yann is long gone. It was raised in 1930 and salvaged, its bell a rare memento of one of the most remarkable days in maritime history. And a day not without bloodshed: nine German sailors died that day, the last casualties of the First World War.

Yet the scuttling, on June 21, 1919, sparked a bonanza of salvaging, with more than 400,000 tonnes of material and 52 vessels on the seafloor. One of the four Koenigs was raised. The other three and the Karlsruhe lie, rusting, under the sea between Hoy and the Orkney mainland. There are three other ships in Scapa Flow but they are not for sale.

The initial salvaging even saw coal from the ships brought to the surface with one entrepreneur buying 26 battleships for just £250.

Now the value of the wrecks is as a tourist destination.

The selling agent has described the unusual offering as “a once in a lifetime opportunity” for a new owner able to tap into the diving holiday market.

Currently recreational divers are allowed to access the waterspace around the wrecks, but are not permitted to touch, enter or to go within one metre of them.

New owners would have the right to dive on the ships, including touching and entering, and would also be able to reclaim items from within – subject to gaining permission from the heritage body Historic Environment Scotland.

Each boat is a Scheduled Monument according to the Ancient Monuments and Archaeological Areas Act 1979 and there is currently a desire to include them in a Historic Marine Protected Area. It is unlikely commercial salvage would be permitted, according to the selling agent. And even a century after the event, this is a sensitive site – any sale would also require consent from the Ministry of Defence.