Sunken giant at the bottom of the Aegean: The Britannic, a diver’s paradise, provides clues to mysteries of the Titanic.

Editor's Note: An earlier version of this article stated that the Britannic was a Victorian-era ship. This is incorrect; the Britannic, along with her sister-ship Titanic, both set sail during the Edwardian era.

Kea, Greece – A hundred years after it sank in the Aegean, the Britannic is shedding light on what sent its doomed sister-ship, the Titanic, to the bottom of the Atlantic, as well as creating a new diving industry in Greece.

The HMS Britannic had been serving as a World War I hospital ship when it struck a German mine five kilometres off the island of Kea, 60km southeast of Athens, in November 1916. The ship sank in just 55 minutes.

Leading up to the November 21 centenary of the sinking, applications for diving permits have soared and the Greek government wants the 49,000-tonne wreck, the largest in the world, to become the centrepiece of a series of marine museums across the country.

“[It] will be the first underwater historical museum in Greece with international importance,” says Angeliki Simosi, head of Greece’s underwater antiquities department.

The reason why: Because the Britannic may hold the key to how and why the Titanic sank in 1912.

The Britannic’s keel was laid at the Harland and Wolff shipyards in Belfast, just five months before the Titanic was launched. The ship was barely taking shape when the Titanic went down, and the disaster threw the shipyard into a crisis of confidence.

“These [ships] were technological firsts. They were the first ships ever this big,” says Richie Kohler, who has made two documentaries about the Britannic. “They were extending the known abilities of engineering, given their ability to understand the tensile strength and things like that.”

The Titanic – a ship once deemed ‘unsinkable’ – went down in the Atlantic after a fateful collision with an iceberg in 1912 [Omikron Omikron/Getty]

Kohler and his team started diving on the Britannic 10 years ago “to chase down a theory that the builders were afraid the Titanic had a failure, that they were correcting that failure on the Britannic, that they were trying to cover up the possibility that the Titanic was a weak ship. The only way to do that was to go down and see the design changes that were made on the Britannic,” Kohler says.

Some of those design changes are well-known. The Titanic’s double hull only extended across the bottom of the ship, defending the deep-drafted vessel against scraping the seabed. The iceberg had cut just below the waterline, where the ship’s skin was vulnerable. The Britannic was widened by half-a-metre so that a double skin could be installed along two-thirds of its length, protecting the boilers and engine rooms.

As the Titanic flooded, the water rose to overwhelm the bulkheads separating its compartments, spilling into one compartment after another. The Britannic’s bulkheads were raised all the way to the bridge deck.

Most important of all: the Britannic rectified the lack of lifeboats on the Titanic. Four enormous gantry davits were added to the decks capable of launching 44 lifeboats on both sides of the ship simultaneously.

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“The Britannic would have survived the damage which the iceberg inflicted on the Titanic,” says historian Simon Mills, who bought the wreck of the Britannic 21 years ago, but Kohler and his team discovered an additional, more subtle improvement, which may suggest that the builders had deeper concerns that the Titanic may have been doomed owing to a design flaw.

During British and American inquests into the Titanic’s sinking, the question of whether it had broken up at the surface was raised. The reports were inconclusive.

In 1986, oceanographer Robert Ballard discovered the Titanic on the Atlantic sea floor and found that the ship was indeed broken into two.

“Where did the Titanic crack in half? Right at an expansion joint,” says Kohler, who was on Ballard’s expedition.

Naval engineer Roger Long has since suggested that the joints, which absorbed metal expansion owing to heat and stress from high seas, were poorly designed.

If true, the Olympic, the Titanic’s predecessor, and the Britannic, its successor, also suffered from the same fatal flaw.

“Roger Long’s theory is that if any of the Olympians had got into a storm with 40ft waves, they would have broken in half on the surface,” says Kohler, of the three ships. He discovered in 2009 that “Britannic’s expansion joints were different”.

The design change may suggest that while the Titanic and the Britannic were meant to stay afloat with six compartments flooded, Harland and Wolff may have suspected that their expansion joints couldn’t withstand the stress of having half of the ship flooded and the other buoyant.

“At about 15 degrees, [the Titanic] went from being intact to breaking apart,” believes Kohler.

Why did it sink?

Given the Britannic’s design improvements, why it sank remains a mystery. It is understood that the German mine it hit caused much more significant damage than the “pokes and stabs” the iceberg inflicted on the Titanic.

“They worked out that the hole that sank the Titanic amounted to about 1.5 square metres,” says Mills. “On the Britannic, the scale of the damage was much, much bigger.”

A giant crane lowers a 490-tonne boiler into Britannic’s hull [Courtesy Simon Mills]

The admiralty’s official report of the sinking says: “There seems to have been a period of one to two minutes from the time of the explosion until the water in the stokeholds was too deep for work to be performed.” In other words, the massive boilers in forward holds 5 and 6, an area measuring 10.6m x 27.4m, were overwhelmed almost instantaneously.

“The mine hit in the worst possible place at the worst possible time. All those watertight doors down below were open because they were changing watch at eight o’clock in the morning. Those doors should have been closed,” says Mills.

In his own report of the incident, Captain Charles Bartlett says orders were “rung below to close watertight doors”. This should have prevented the cross flooding of the holds.

“For some reason, the doors in the forward part of the ship didn’t close,” says Mills. Even if electrical switches failed, the doors had manual levers. Failing that, a float mechanism should have triggered them.

Captain Bartlett reports that after the explosion, the ship started “trembling and vibrating most violently fore and aft, continuing for some time”.

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Underwater museum

The idea of an underwater museum was mooted as early as 1963, but was only legislated in 2013. More than 1,000 wrecks have been mapped in the Greek seas and some are already designated museums, but Kea dreams of becoming a global underwater World War I museum with three wrecks.

The Burdigala, a French steamer that sank while serving as a troop carrier just a week before the Britannic, lies at a depth of 75m.

“It is intact. It was discovered eight years ago,” says diver Yiannis Tzevelekos. “It really is like being in an underwater museum. You can see the telegraph, Marconi, ship’s bell and chandeliers all in place … It’s also upright, as though a human hand has placed it in a sailing position.”

Between the Burdigala and the Britannic, at just 35 metres, lies the Patris, a Greek storm-sunk steamer with one of its paddle wheels still in place. All are to become part of Kea’s network of underwater galleries.

“Mass tourism isn’t interested in small destinations. If a place can show that it has a different profile, then it can claim a piece of the market,” says Mayor Yiannis Evangeliou, who has spent four decades in the tourism industry. He plans to go further, and create a marine wildlife park for less experienced divers.

Vintage maritime history photo of the RMS Titanic’s propellers as the ship sits in dry dock [John Parrot/Stocktrek Images/Getty]

The beauty of the Britannic

Technical divers who have braved its 120-metre depth to see the Britannic’s hulk stretching almost a third of a kilometre in the gloom, speak of it with awe. Jacques Cousteau, the first to visit the ship in 1976, allegedly said that “diving across the Britannic is like being a flea on the back of an elephant”.

“What takes your breath away is the sheer size of the shipwreck,” says Leigh Bishop, one of the world’s most experienced deep-sea wreck divers. “You’re physically in touch with one of the Olympic Star liners. Where else can you effectively dive down to the Titanic?”

“On the Titanic, you’re painfully aware that 1,500 people died. It is a dark, barren, lifeless ship,” says Kohler. “When you go to the Britannic it is bathed in beautiful light; it is such a comfortable, warm, blue-green … covered with growth and corals and sponges and fans, and everything is striving for light and life.”

The Britannic had its own tragedy. As it evacuated a thousand crew members, Captain Bartlett tried to beach it on Kea. The ship had already begun to list to starboard, and the port propeller hung half out of the water as it roared to life. “Two boats were pulled into the turning propeller, and they were smashed to matchwood. Thirty people were killed and 30 or 40 were very seriously injured,” says Mills.

The Britannic is important beyond its casualties and the light it sheds on what happened to the Titanic. The ultimate Olympic class liner, it carried the largest boilers and steam-driven engines ever built before or since.

Its speed of 20 knots was unprecedented for its size. It was then the safest passenger vessel ever built. The Harland and Wolff launch booklet called it “both in design and construction, as perfect a specimen of man’s creative power as it is possible to conceive”.

Yet, this pinnacle of Edwardian technology was rapidly overtaken by events. It never served as a passenger liner. Its life as a hospital ship lasted just 11 months. The Britannic, perhaps more than any physical object, lies as a testament to how shockingly and irreversibly the Great War changed the world.